Wound cleansing apparatus with heat

ABSTRACT

An apparatus for cleansing and promoting tissue growth in wounds, in which irrigant fluid optionally containing cell nutrients and/or other physiologically active material from a reservoir connected to a conformable wound dressing and wound exudate from the dressing are recirculated by a device for moving fluid through a flow path which passes through the dressing, a biodegradable scaffold in contact with the wound bed and a means for fluid cleansing and back to the dressing. The apparatus has means for supplying thermal energy to the fluid in the wound. The cleansing means (which may be a single-phase, e.g. micro-filtration, system or a two-phase, e.g. dialytic system) removes materials deleterious to wound healing, and the cleansed fluid, still containing materials that are beneficial in promoting wound healing, is returned to the wound bed. The dressing and a method of treatment using the apparatus.

The present invention relates to apparatus and a medical wound dressingfor irrigating, supplying thermal energy to and cleansing wounds, and amethod of treating wounds using such apparatus for irrigating, supplyingthermal energy to and cleansing wounds.

It relates in particular to such an apparatus, wound dressing and methodthat can be easily applied to a wide variety of, but in particularchronic, wounds, to cleanse them of materials that are deleterious towound healing, whilst retaining materials that are beneficial in sometherapeutic aspect, in particular to wound healing.

Before the present invention, aspirating and/or irrigating wounds andapparatus therefor were known, and tended to be used to remove woundexudate during wound therapy. In known forms of such wound therapy, theofftake from the wound, especially when in a highly exuding state, isvoided to waste, e.g. to a collection bag.

Materials deleterious to wound healing are removed in this way.

However, materials that are beneficial in promoting wound healing, suchas growth factors, naturally occurring anti-inflammatories, and otherphysiologically active components of the exudate from a wound are lostto the site where they can be potentially of most benefit, i.e. thewound bed, when such therapy is applied.

It thus would be desirable to provide a system of therapy which

-   a) can remove materials deleterious to wound healing from wound    exudate, whilst retaining materials that are beneficial in promoting    wound healing in contact with the wound bed, and/or-   b) which allows fluids containing active amounts of materials that    are beneficial in promoting wound healing to pass into and/or    through the wound in contact with the wound bed.

Dialysis is a known method of treating bodily fluids such as blood exvivo, to cleanse them of materials that are deleterious to the bodysystemically. Retaining materials that are beneficial in sometherapeutic aspect in the treated fluid is not an object of dialysis.

This method of treating bodily fluids is also a systemic therapy, sincethe treated fluid is returned to within the body. This is in contrast toa topical therapy in which the treated fluid is recycled outside thebody, e.g. to a wound.

Dialysis also requires large amounts either of bodily fluids, such asblood, or of dialysate, and consequently the relevant devices tend notto be portable.

Even when in a highly exuding state, chronic wounds produce relativelylittle fluid to be treated and relatively little materials that arebeneficial in some therapeutic aspect to be retained in the wound and/orits environment.

It is an object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known aspiration and/or irrigation therapy systems, and-   b) to provide a system of therapy which can remove materials    deleterious to wound healing from wound exudate, whilst retaining    materials that are beneficial in promoting wound healing in contact    with the wound bed,

It is a further object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known dialysis systems, and-   b) to provide a system of therapy which can remove materials    deleterious to wound healing from wound exudate, whilst retaining    materials that are beneficial in promoting wound healing in contact    with the wound bed,-   c) without affecting the body systemically.

It is a yet further object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known dialysis systems, and-   b) to provide a system of therapy which can remove materials    deleterious to wound healing from wound exudate, whilst retaining    materials that are beneficial in promoting wound healing in contact    with the wound bed,-   c) without affecting the body systemically, and-   d) which is portable.

Additionally, it is generally believed that the body's own metabolicactivities are at an optimum at or near the temperature naturallyoccurring in the relevant bodily part.

Examples of metabolic molecules involved in tissue healing processesthat are beneficial in promoting wound healing include enzymes, growthfactors and anti-inflammatories, and other physiologically activecomponents of the exudate from a wound.

These are believed to act best at temperatures found in the relevantbodily part in which they occur, varying between normal temperaturesfound at the body surface and those at the body core.

The body core is at a higher temperature than the surface, but surfacetemperatures at 33° C. and above are still relatively close to core bodytemperatures of 36 to 38° C. (‘normothermic temperature’). Wounds, andin particular chronic wounds, may have a lower temperature, e.g. 24 to26° C., i.e. substantially below the optimum temperature. Thus, thetemperature of the wound itself is deleterious to wound healing.

This may result in slow wound healing, loss of cell proliferation,and/or growth that does not have a strong three-dimensional structureadhering well to and growing from the wound bed.

Conventional wound aspiration and/or irrigation therapy systems thusoften create a wound environment under a backing layer where

-   a) not only are beneficial materials lost to the site where they can    be potentially of most benefit, i.e. the wound bed, when such    therapy is applied, but-   b) the wound healing processes, e.g. enzymic activity on tissue    growth, are inhibited by sub-optimal temperatures.

Heated dressings are known, but such forms of wound dressing do notsimultaneously irrigate the wound environment under the backing layer.

This will result in materials deleterious to wound healing in woundexudate being retained in the wound environment and hindering woundhealing in spite of any stimulation of wound healing from woundtemperature regulation.

There would thus be an advantage, in particular in chronic wounds, inproviding means for more than one therapy in a single dressing.

-   a) which not only removes materials deleterious to wound healing    from wound exudate, whilst retaining materials that are beneficial    in promoting wound healing in contact with the wound bed, but-   b) promotes wound healing by creating a wound environment under the    dressing with temperatures which stimulate the activity of metabolic    molecules that are beneficial in promoting wound healing, e.g.    temperatures near 36 to 38° C. (‘normothermic temperature’).

It is an object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known wound dressing, and-   b) to provide a system of therapy which cleanses wounds, but also    supplies thermal energy to the wound. in particular one which    -   i) can remove materials deleterious to wound healing from wound        exudate, whilst retaining materials that are beneficial in        promoting wound healing in contact with the wound bed, and    -   ii) maintains wounds at or near normothermic temperature,

It is an object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known wound dressing, and-   b) to provide a system of therapy that conveniently cleanses wounds,    but also maintains wounds at or near normothermic temperature.

A disadvantage of known heated wound dressings is that it is imperativebut not easy to avoid the heater, especially an electrical heater, fromscorching the wound and/or surrounding surfaces. This is especially sowhen the dressing is in contact with the wound bed.

Several devices for applying to the wound to try to do so have beenproposed. In one form, a stiff flange or lip extends around theperiphery of the dressing to space the surface of the wound in use awayfrom the heater. Such a wound dressing is cumbersome. Whilst it may beacceptable for hospital use, the stiff flange does little for patientcomfort, and heightens the risk of inflammation of a wound and/or theleakage of wound exudate. There would be a further advantage inproviding such a wound dressing that conforms to the shape of the bodilypart to which it is applied.

It is an object of the present invention

-   a) to obviate at least some of the abovementioned disadvantages of    known wound dressing, and-   b) to provide a system of therapy which    -   i) can remove materials deleterious to wound healing from wound        exudate, whilst retaining materials that are beneficial in        promoting wound healing in contact with the wound bed,    -   ii) which supplies thermal energy to and/or through the wound,        and    -   iii) comprises a conformable wound dressing.

Thus, according to a first aspect of the present invention there isprovided an apparatus for irrigating, supplying thermal energy to, andcleansing wounds, characterised in that it comprises

-   a) a fluid flow path, comprising    -   i) a conformable wound dressing, having        -   a backing layer which is capable of forming a relatively            fluid-tight seal or closure over a wound and        -   at least one inlet pipe for connection to a fluid supply            tube, which passes through and/or under the wound-facing            face, and        -   and at least one outlet pipe for connection to a fluid            offtake tube, which passes through and/or under the            wound-facing face,        -   the point at which the or each inlet pipe and the or each            outlet pipe passes through and/or under the wound-facing            face forming a relatively fluid-tight seal or closure over            the wound,        -   at least one inlet pipe being connected to a fluid            recirculation tube, and at least one outlet pipe being            connected to a fluid offtake tube: and    -   ii) a means for fluid cleansing having at least one inlet port        connected to a fluid offtake tube and at least one outlet port        connected to a fluid recirculation tube;-   b) a fluid reservoir connected by a fluid supply tube to an integer    of the flow path (optionally or as necessary via means for flow    switching between supply and recirculation);-   c) a device for moving fluid through the wound dressing and means    for fluid cleansing, and optionally or as necessary the fluid supply    tube;-   d) the apparatus having means for supplying thermal energy to the    fluid in the wound,-   and-   e) optionally means for bleeding the flowpath, such that fluid may    be supplied to fill the flowpath from the fluid reservoir via the    fluid supply tube (optionally or as necessary via the means for flow    switching) and recirculated by the device through the flow path.

Where any pipe is described in connection with the operation of theapparatus as being connected or for connection to a (mating end of a)tube, e.g. a fluid supply tube, fluid recirculation tube or fluidofftake tube, the pipe and the tube may form a single integer in theflow path through which the circulating fluid from the wound passes.

An advantage of such wound dressings is that it is easy to avoidoverheating of the wound and/or surrounding surfaces, especially byelectrical heating, since the heating must always pass to the woundthrough a heat transfer medium (the irrigant). This eliminates directcontact of the wound bed with the heater, and irrigant may be used as aheat transfer medium in a highly controllable manner.

The apparatus is most favourable to the wound healing process in chronicwounds, and thus for irrigating, supplying thermal energy to, andcleansing wounds such as diabetic foot ulcers, and especially decubituspressure ulcers.

However, thermal energy may also appropriately be applied using theapparatus to aid the healing process in other wound types, such as acuteand/or surgical wounds, including burns.

In a preferred mode, the present invention is used to provide a systemof therapy which conveniently cleanses wounds, but also maintains themat or near normothermic temperature.

Accordingly a preferred type of the apparatus of the invention forirrigating, supplying thermal energy to and cleansing wounds is providedwith means for maintaining the wound at or near normothermictemperatures.

As noted above, the apparatus of the present invention for irrigating,supplying thermal energy to, and cleansing wounds has a direct effect onactive components of fluid in contact with the wound, in particularsolutes or disperse phase species that are beneficial in promoting woundhealing that are in contact with the wound bed. Additionally, cellmitochondria aid proliferation and hence wound healing, in particular inchronic wounds, and are stimulated by near infrared radiation.

Application of such radiation to the wound resulting in an increase incell proliferation in the tissue underlying to the wound, and in thebreaking strength of the new tissue.

Other physiologically active components of the cells in the tissueunderlying the wound that are beneficial in promoting wound healing mayalso be stimulated by radiation on the wound.

Examples of means for supplying thermal energy to the fluid in the woundinclude as may be appropriate conducted thermal energy, electromagneticradiation of an appropriate wavelength, or (less often) as convectedthermal energy.

In the present apparatus, heat will usually be conducted to the woundbed by the irrigant and/or wound exudate within the dressing.

However, thermal energy may as appropriate be supplied to the irrigantand/or wound exudate within the dressing, and may be applied to thefluid by any suitable means, at any suitable point, often depending onparticular components and/or materials that are used.

Examples of such means include

-   a) direct conductive contact of the irrigant and/or wound exudate    with a heater and/or conductively heated component of the apparatus    flow path;-   b) direct electromagnetic irradiation at an appropriate wavelength,    e.g. infrared and/or near infrared from a radiative heater of the    irrigant fluid and/or wound exudate; and/or-   c) electromagnetic irradiation from a radiative heater of a    component of the apparatus flow path that absorbs electromagnetic    irradiation at an appropriate wavelength, e.g. infrared and/or near    infrared and is in direct conductive contact with the irrigant    and/or wound exudate.

Accordingly, one embodiment of the present apparatus for irrigating,supplying thermal energy to and cleansing wounds supplying thermalenergy to and cleansing wounds is characterised in that it comprisesmeans for providing thermal energy to the fluid in the wound.

Another embodiment of the present apparatus for irrigating, supplyingthermal energy to and cleansing wounds is characterised in that itcomprises means for supplying electromagnetic radiation of anappropriate wavelength to the fluid in the wound.

Another embodiment of the present apparatus for irrigating, supplyingthermal energy to and cleansing wounds is characterised in that itcomprises means for supplying electromagnetic radiation of anappropriate wavelength to the fluid in the wound.

The heater of the irrigant fluid and/or wound exudate and/or heatedcomponent of the apparatus flow path may be at any convenient orappropriate position or component of the apparatus flow path.

Examples include a heater and/or conductively heated component of theapparatus flow path

-   a) mounted distally of the body on, in or inside of the dressing;-   b) mounted in, on, at or near one or more of the fluid inlet pipe(s)    and outlet pipe(s) that pass through and/or under the wound-facing    face of the backing layer;-   c) mounted in, on, at or near one or more of the connectors in the    tubes that form the flow path of the apparatus;-   d) mounted in, on, at or near the reservoir; and/or-   e) mounted in, on, at or near the means for fluid cleansing.

As noted above, the irrigant and/or wound exudate fluid in the interiorof the wound dressing is beneficially maintained at a temperature thatis at or near the temperature naturally occurring in the relevant bodilypart and/or normothermic temperature.

The desired or optimum temperature of the wound will substantiallydetermine

-   a) the position along the apparatus flow path or the component of    the apparatus flow path where the heater and/or conductively heated    component of the apparatus flow path is mounted relative to the    dressing;-   b) the flow rate of irrigant fluid and/or wound exudate;-   c) the temperature to which the point of supply of thermal energy to    apparatus is raised;-   d) the thermal insulation of the system in which the fluid    recirculates and heat is conducted to the wound; and/or-   e) the nature of the heater.

In examples of direct conductive contact of the irrigant and/or woundexudate with a heater and/or conductively heated component of theapparatus flow path, the heater may be or be connected to a heatexchanger mounted in conductive contact with irrigant and/or woundexudate at an appropriate point in the system in which the fluidrecirculates and heat is conducted to the wound.

The heat exchanger may comprise an array of thermally conductiveextended surfaces, such as fins, baffles or other like structures ofconductive material in a more convoluted form with a relatively largesurface area.

These transfer thermal energy when a temperature drop is applied overthem, mounted in conductive contact with irrigant and/or wound exudate,with spaces therebetween such that wound irrigant and/or wound exudatemay recirculate through the spaces.

Alternatively, where appropriate it may be provided in the form of alike array of conductive hollow structures, such as pipes, tubes orother like structures in the apparatus flow path, through which a heatexchanger fluid recirculates and transfers heat from a heat source to beconducted to the wound.

The array of conductive hollow structures may consist essentially ofsmall apertures or pores that may form such bores, channels, conduitsand/or passages through a heated metal sinter, such as one of e.g.stainless steel, mounted in conductive contact with irrigant and/orwound exudate in the apparatus flow path, through which the fluidrecirculates, so that heat is conducted to the wound.

Such a heat exchanger may be outside the wound space and the backinglayer or within the wound space and under the backing layer. If outsidethe wound space and the backing layer, it is preferably as close to thewound dressing backing layer as possible.

This is especially the case where the apparatus of the invention forirrigating, supplying thermal energy to and cleansing wounds is intendedto maintain the wound at or near normothermic temperatures, since theheating must always pass to the wound through heat transfer via theirrigant and/or wound exudate recirculated through the wound space, andthe longer the connection to the inlet pipe(s) on the wound dressing andthe dwell time of the irrigant therein, the greater the undesired lossof heat from the irrigant fluid. It may be mounted outside the backinglayer, e.g. 6 to 90 mm from the wound bed, e.g. on an inlet pipe and/ora fluid recirculation tube.

Where the heat exchanger is mounted outside the wound space and thebacking layer, and transfers heat from a heat source to wound irrigantand/or wound exudate recirculating through the space, to be conducted towound, the apparatus flow path, through which irrigant and/or woundexudate recirculates, at an appropriate point in the heat exchanger maybe provided in the form of a conductive hollow structure in convolutedform with a relatively large surface area.

This transfers thermal energy from the heater and/or a heat exchangerfluid recirculated in conductive contact with it to the irrigant to beconducted to the wound.

In examples of such conductive contact of the irrigant and/or woundexudate with a heater and/or heat exchanger mounted, the apparatus flowpath may be in convoluted form with a relatively large surface area,such as one or more pipes, tubes or other like structures, asappropriate ‘in parallel’ and/or with spaces therebetween, in the formof a spiral, helix or spiral helix, or loop or a more convoluted form,e.g. a meandering, tortuous, winding, zigzag, serpentine orboustrophedic (i.e. in the manner of a ploughed furrow) pattern, inparticular a conductive hollow spiral.

Such a part of the flow path of the apparatus may be in directconductive contact with a heater and/or conductively heated component,e.g. a conductive hollow spiral part of the flow path of the apparatusmay within a moulded disc-shape housing defined by a film, sheet ormembrane that

-   a) has a heater and/or conductively heated component in direct    conductive contact with and on at least one surface of the    conductive hollow spiral part of the flow path, e.g. an electrically    heated element mounted in an insulated so-called clamshell case, or-   b) contains a heat exchanger fluid recirculated between spaces    between turns of the spiral to which it is applied.

A pre-formed spiral of tubing is housed in the heater case, which ispreferably a rigid integer for convenient handling, which is thenclosed.

An apparatus flow path in a heat exchanger in the form of a helix orspiral helix, or loop or a more convoluted form, may also be in directconductive contact with and within an appropriate moulded housingsimilarly provided in a form which transfers thermal energy from aheater and/or a heat exchanger fluid recirculated in conductive contactthrough it.

Alternatively, where appropriate, a flow path through which a heatexchanger fluid recirculates, e.g. a pre-formed spiral of tubing, maylie in spaces between and/or adjacent to turns or ‘in parallel’ arms ofthe apparatus flow path, and so transfer heat from a heat source to theirrigant and/or wound exudate flow. The whole may be loaded into aheater case, which is then closed. The flows of the heat exchanger fluidand the irrigant may be in a co- or preferably counter-currentdirection.

In all embodiments, the case has entry and exit apertures, holes,openings, orifices, slots, channels and/or conduits, e.g. in the edgeextending between the faces of the case, through which the irriganttubing passes, and into which it may be sealed or otherwise attached,for example by heat-sealing, and where it may be connected to otherintegers of the flow path.

Rather than using tubing, e.g. a conductive hollow spiral to define atortuous path through which the irrigant is forced to flow in part ofthe flow path of the apparatus within a heat exchanger, it may berecirculated in conductive contact through one or more channels,conduits or passages or other like structures, as appropriate ‘inparallel’ and/or with spaces therebetween.

It or they may be in the form of a spiral, loop or a more convolutedform, e.g. a meandering, tortuous, winding, zigzag, serpentine orboustrophedic (i.e. in the manner of a ploughed furrow) pattern, asappropriate ‘in parallel’ and/or with spaces therebetween.

This shape arrangement may, e.g. be made by sealing two flexible films,sheets or membranes together along lines of contact to form a convolutedflow path within a sealed chamber. This flow path is defined by one ormore channels, conduits or passages or other like structures in atortuous path through which the irrigant is forced to flow in part ofthe flow path of the apparatus, in particular in a boustrophedic (i.e.in the manner of a ploughed furrow) pattern. It may be made by sealingby a suitable method (e.g. radio frequency or impulse heat welding.

It or each is in conductive contact, preferably throughout its length,with a heater on at least one surface of the films defining the part ofthe flow path, e.g. an electrically heated element. The whole may beappropriately mounted in a case, bag, chamber or pouch of conventionaltype, such as a pouch or other structure, e.g. of polymer, which cancontain the heater and/or heat exchanger, which is preferably a rigidinteger to provide for convenient handling.

Alternatively, where appropriate, a flow path through which a heatexchanger fluid recirculates may be made to lie in spaces between and/oradjacent to turns or ‘in parallel’ arms of the apparatus flow path, andso transfer heat from a heat source to the irrigant and/or wound exudateflow. The whole may be appropriately housed in a case, bag, chamber orpouch of conventional type, as above. The flows of the heat exchangerfluid and the irrigant may be in a co- or preferably counter-currentdirection.

In all embodiments, the or each channel, conduit or passage or otherlike structure, will as appropriate at its inlet and outlet communicatewith and be connected to a tube, pipe, duct or other like structurewhich in turn communicates with and is connected to other integers ofthe flow path, e.g. an irrigant feed pump.

The case, bag, chamber or pouch of conventional type, as referred toabove has at least one entry and exit aperture, hole, opening, orificeand/or slot, through which the tubes, pipes, ducts or other likestructures pass, and into which they may be sealed or otherwiseattached, for example by heat-sealing.

For convenient handling in use, the case, bag, chamber or pouch ofconventional type is adapted to fit as closely as possible into areceiving aperture, hole, opening, orifice and/or slot in a heat sourceto transfer heat to the irrigant in the apparatus flow. For example, theflat structures described by way of example above as suitable for use inthis integer of the present invention may be sandwiched between parallelelectrically heated plates.

It is preferably locked in position such that it cannot be dislodgedaccidentally in normal use, but can easily be removed when required.

For convenient handling in use, the heating device itself, into whichthe pouch is inserted, may be mounted securely on the patient and/or thewound dressing (if it is as close as possible to, e.g. 6 to 900 mm fromthe wound bed, e.g. on an inlet pipe and/or a fluid recirculation tubeto reduce undesired loss of heat from the irrigant).

The means for providing thermal energy to the fluid in the wound maysuitably comprise one or more such heater and/or heat exchanger modulesconnected in series and/or in parallel arms of the apparatus flow path.

Some of the factors likely to affect heat transfer in all embodiments ofthe exchanger are

the temperature of the heater element,

the structure and material appropriate to the heat exchanger and anyheat exchanger fluid,

the wall thickness and surface area in contact with the heater of anypipe, tube, channel, conduit, passage or other like structure,

the length of irrigant flow path and the irrigant linear flow rate,

the length of any heat exchanger fluid and any heat exchanger fluid flowrate, and

whether any heat exchanger fluid and the irrigant flow are in co- orcounter-current directions, as will be apparent to the skilled person.

The structure for holding irrigant in contact with the heater maysuitably be a pipe, tube, channel, conduit, passage or the like. Such astructure may be a pipe, tube, channel, conduit, passage or the like onand integral with a face of the heater, which may be, e.g. anelectrically heated plate, so that the irrigant and/or wound exudaterecirculates in direct conductive contact with the heater in the heatexchanger. Alternatively or additionally, it may be in the form of adiscrete pipe or tube permanently or releasably attached to at least oneface of the heater, which again may be, e.g. at least one electricallyheated plate, so that the irrigant and/or wound exudate recirculates inindirect conductive contact with the heater in the heat exchanger.

In either case, the walls of any pipe, tube, channel, conduit, passageor other like structure for irrigant in contact with the heater maysuitably be no more than 600 micron thick. Where it is in contact withany pipe, tube, channel, conduit, passage or other like structure forheat exchanger fluid the combined thickness of the walls may suitably be10 to 500 micron. When heat exchanger fluid and the irrigant flow are incounter-current directions, the thickness may be increased.

The surface area of any pipe, tube, channel, conduit, passage or otherlike structure for irrigant and/or wound exudate flow in contact withthe heater or any pipe, tube, channel, conduit, passage or other likestructure for a heat exchanger fluid (including those in a heated metalsinter) may suitably be no less than 100 mm², such as 625 to 2500 mm²,e.g. up to 6400 mm².

Any pipe or tube, or any films, sheets or membranes sealed togetheralong lines of contact to form a convoluted irrigant flow path, such asa channel, conduit, passage or other like structure may be ofthermoplastic polyurethane or PVC but other materials may be used (e.g.thermoplastic elastomers), provided they are of suitable strength andflexibility and/or rigidity to provide for convenient handling, clearedfor medical use and fulfil the desired performance specification.

The length of irrigant flow path, such as in the structures described byway of example above as suitable for use in this integer of the presentinvention may suitably be no less than 10 mm, such as

25 to 1600 mm, e.g. up to 2500 mm in the case of a 1.5×2.7 mm tube withflow rates of up to 400 ml/hr,

up to 750 mm in the case of a similar channel defined by two weldedfilms, and up to 360 mm in the case of a similar channel integral with aheater face as described hereinbefore,

depending on particular components and/or materials that are used and onthe surface area noted above.

For larger surface area of any pipe, tube, channel, conduit, passage orother like structure for irrigant flow, the length of irrigant flowpath, e.g. in the structures described above may suitably be more than2500 mm, such as (by way of example only) 4000 mm.

The volume flow rate of irrigant and/or wound exudate in recirculationthrough the means for providing thermal energy to the fluid in the woundmay suitably and typically be the same as in the rest of the system inwhich the fluid recirculates, as described below. That is, of the orderof 1 to 10 ml/cm²/24 hour, where the cm² refers to the wound area, e.g.1 to 750 ml/cm²/hour, such as 1 to 500 ml/hr.

However, the cross-sectional area of any pipe, tube, channel, conduit,passage or other like structure for irrigant in the means for providingthermal energy to the fluid may be adjusted to increase or decrease theirrigant linear flow rate for the desired performance specification. Toachieve the target temperature at the heater outlet, the irrigant linearflow rate in a typical heat exchanger with the irrigant flow path in thestructures described above may suitably be 1 to 600 mm/s, e.g. up to 370mm/s.

The surface area and the irrigant linear flow rate and length ofirrigant flow path all depend inter alia on the particular target woundtemperature and temperature at the heater outlet. Those noted above aregenerally suitable for use in this integer, where the temperature of thewound is to be held within a range of temperatures such as 34 to 40,preferably 35 to 39, and optimally 36 to 38° C. at the wound bed,preferably at normothermic temperatures, throughout the use of thepresent apparatus for irrigating, supplying thermal energy to andcleansing wounds.

Depending inter alia on the particular target wound temperature and theloss of heat from the irrigant between the means for providing thermalenergy to the fluid and the wound dressing (especially if it is not asclose as possible to, e.g. more than 6 to 900 mm from the wound bed),the temperature of irrigant leaving the heater will often convenientlybe fixed at 39° C.+/−3° C., independently of flow rate, in particular tomaintain an at or near normothermic temperature within the dressing,especially for chronic wounds.

The exit temperatures may of course be adjusted to increase or decreasewound temperatures, by adjusting the foregoing parameters, such asincreasing or decreasing the irrigant linear flow rate for the desiredtemperature specification.

For example, with the flat structure heating pouch design described byway of example above as suitable for use in this integer and electricalheater (heating from only one side) it was found possible to maintain anirrigant temperature at the heater outlet of ˜37° C. at irrigant ratesof up to ˜400 ml/hr.

This allows the liquid entering the wound to be as close as possible tothe patient core temperature of ˜37° C., and so help maintainnormothermia. The area of pouch in contact with the heater was ˜750 mm².To achieve the target temperature at the heater outlet at the highestflow rate, the heater was required to operate at a temperature ofapproximately 42° C.

All the foregoing means for providing thermal energy to the fluid andthe wound dressing are especially (but not exclusively) suited to directconductive contact of the irrigant and/or wound exudate with a heaterand/or other conductively heated component. Various embodiments ofheaters as a component of the apparatus flow path of the presentapparatus for irrigating, supplying thermal energy to and cleansingwounds will now be described in detail hereinafter.

Examples of conductive heaters include:

-   a) an electric heater mounted in conductive contact with irrigant    and/or wound exudate (but electrically insulated from the fluid and    the system in which the fluid recirculates and heat is conducted to    the wound).    -   The heater may inter alia comprise:    -   i) an array of electrically resistive but conductive wires,        fibres, filaments, strands or other like structures that        generate thermal energy when a voltage drop is applied over        them.        -   The array may be a parallel array with spaces therebetween,            and the wound irrigant and/or wound exudate may recirculate            through the spaces.        -   Alternatively, where appropriate it may be provided in the            form of non-woven or woven fabric, such as a woven layer or            sheet. This may as appropriate be used essentially as a flat            sheet or membrane of material in a more convoluted form,            e.g. conformed to the form of other structures such as            pipes, tubes, etc. in the apparatus flow path, as a duct,            sheath, or casing, or other like structure.        -   Depending on any pressure differential across it may require            other materials on or in it to stiffen, reinforce or            otherwise strengthen it.        -   The material of the heater may have a positive or (less            preferably) a negative thermal coefficient of resistance.        -   A control feedback circuit is needed with a negative            coefficient of resistance for temperature regulation.        -   Materials that are described by way of example herein to be            suitable for use in this aspect of the present invention            will be capable of this function.        -   Depending on other components and/or materials that are            present, examples of suitable materials include carbon            fibres and fabric, such as a woven layer or sheet, which may            as appropriate be made essentially of carbonised acrylate,            such as polyacrylonitrile and copolymers thereof.    -   ii) an electrically insulating flat sheet or membrane substrate        that has sites on its surface that are connected by an array of        electrically resistive but conductive tracks, traces, outlines,        or other like structures, e.g. filled channels, conduit and the        like, and, e.g. etched foil, which generate thermal energy when        a voltage drop is applied over them.        -   The array may be a parallel array with spaces therebetween,            connected together at each end, or comprise or consist            essentially of one or more such integers in a spiral, or in            a meandering, tortuous, winding, zigzag, serpentine or            boustrophedic (i.e. in the manner of a ploughed furrow)            pattern.        -   Examples of suitable materials for the array of electrically            resistive but conductive tracks, traces, outlines, or other            like structures include carbon and/or metals, such as            Thermion™, a nickel-coated non-woven carbon fabric and            resistance heating alloys, such as Kanthal™, Alkrothal™,            Nikrothal™, and Nifethal™.        -   For the electrically insulating flat sheet or membrane            substrate, suitable materials include PTFE, polyamides, and        -   materials such as aromatic polysulphones,            polyethersulphones, polyetherether-sulphones, polyketones,            polyetherketones; and polyetherether-ketones, and            sulphonated derivatives thereof, and mixtures thereof; and            epoxy resins.        -   The array of electrically resistive but conductive tracks,            traces, outlines, or other like structures, may be generated            by etching or engraving, e.g. with electron beam irradiation            and/or with fluid chemicals.        -   Alternatively, where appropriate it may be provided by            printing, imprinting, stamping or vapour deposition of            conventional type.    -   iii) an array of electrically resistive but conductive, mutually        connected thermocouples that are potentially capable of        generating thermal energy by the Peltier effect when a voltage        drop is applied over them.        -   The array may be a parallel array with spaces therebetween,            and the wound irrigant and/or wound exudate may recirculate            through the spaces.        -   Alternatively, it may be permanently or releasably attached            to the surface of a substrate of the type described by way            of example under ii) as suitable for use in this aspect of            the present invention.        -   Depending on other components and/or materials that are            present, examples of suitable materials include            thermoelectric modules comprising pellets of bismuth            telluride doped with selenium and antimony of different            conductivity, the thermocouple pairs being connected in            series and sandwiched between ceramic substrates.        -   In the Peltier effect when a voltage drop is applied over a            thermocouple, one part potentially undergoes heating, and            can thus supply thermal energy to the wound through a heat            transfer medium (the irrigant).        -   The other part undergoes cooling and can thus act as a            thermal pump from the ambient to the fluid irrigant and            exudate in the apparatus flow path to the wound.

However, thermal energy transfer in this highly controllable mannerrequires orientation of the thermocouple array such that the sidecapable of gaining thermal energy by the Peltier effect is in conductivecontact with the irrigant and/or wound exudate.

-   -   -   Examples of a) i) & ii) include a foam reservoir dressing,            such as Allevyn (™, Smith & Nephew) and Tielle (™, Johnson &            Johnson), having an electrical heater, mounted distally of            the body on it.

-   b) an inductive heater element mounted in conductive contact with    irrigant and/or wound exudate (but electrically insulated from the    fluid and the system in which the fluid recirculates and heat is    conducted to the wound).    -   The heater may inter alia comprises a piece of ferromagnetic        material, such as magnetic stainless steel in conductive contact        with irrigant and/or wound exudate, and an inductive source that        will be adjacent (but not necessarily attached) to the dressing        in use, but may otherwise be remote from the wound).    -   Examples of the latter include a ferromagnetic coil, spiral,        helix or spiral helix, or loop or a more convoluted form, e.g. a        meandering, tortuous, winding, zigzag, serpentine or        boustrophedic (i.e. in the manner of a ploughed furrow) pattern,        in particular in one plane, of an inductive often highly        conductive material, connected to an alternating electrical        potential source.    -   This is potentially capable of generating thermal energy in the        core when a varying potential is applied to the coil, spiral or        spiral helix, or loop or a more convoluted form.    -   This is often at mains voltage and frequency, although a range        of either may be used.

-   c) a heater mounted in conductive contact with irrigant and/or wound    exudate to which it transfers thermal energy to the fluid in    recirculation from a heat source within it, which is a fuel cell.    -   In this, atmospheric oxygen and/or other molecules oxidise one        or more species of fuel molecules, often in a catalytic bed.    -   Examples of fuel materials that have a strong oxidation exotherm        include gases, where the gaseous phase of the aerosol system is        air and a fuel gas, such as hydrogen or an alkane, such as        methane, ethane and butane.

The catalyst is often solid particulates, such as composites of copperand rare earth oxides, such as optionally samaria doped ceria. comprisedin a crystalline material for convenient handling; or platinum powdercoated onto carbon paper or cloth.

-   d) a heater mounted in conductive contact with irrigant and/or wound    exudate to which it transfers thermal energy to the fluid in    recirculation from a heat source within it, which is a material that    undergoes a highly exothermal phase change.    -   Examples of d) include    -   i) a heater containing materials that undergo a highly        exothermal crystallisation or solidification phase change, such        as supersaturated solutions of chemicals, such as metal ion        salts.        -   Sodium thiosulphate is a source of a strong crystallisation            exotherm, as is sodium acetate solution.        -   The fluid or solid material is often comprised in one or            more conformable hollow bodies.        -   These may be defined by, for example a polymer film, sheet            or membrane, such as a bag, chamber, pouch or other            structure, of the backing layer, e.g. of polymer film, for            convenient handling.        -   In the case where the heat source is in the form of a            crystallisation system, such as one based on sodium            thiosulphate, the bag, chamber, pouch or other structure is            often provided with a source of mechanical shock that is            appropriate for inducing crystallisation.        -   Examples include a catastrophically resiliently flexible or            stiff metal button, such as one of e.g. aluminium or            stainless steel.        -   Such heaters are less preferred than an electrical heater,            since electrical heating can give constant heating            intensities in a highly controllable manner. In contrast, a            strong crystallisation or solidification exotherm is less            controllable or constant.    -   ii) a heater containing materials that undergo an exothermal        condensation phase change, i.e. from gaseous or volatile        products, such as the Freon hydrocarbon series to liquids.        Preferred materials include, in particular those that condense        at or near normothermic temperature. Such a heater of the        irrigant fluid and/or wound exudate may be operated as a heat        pump that absorbs thermal energy, e.g. from the environment of a        component of the apparatus flow path into the component of the        apparatus flow path.

In examples of

-   a) direct electromagnetic irradiation at an appropriate wavelength,    e.g. infrared and/or near infrared from a radiative heater of the    irrigant fluid and/or wound exudate; and/or-   b) electromagnetic irradiation from a radiative heater of a    component of the apparatus flow path that absorbs electromagnetic    irradiation at an appropriate wavelength, e.g. infrared and/or near    infrared and is in direct conductive contact with the irrigant    and/or wound exudate.    the heater usually works at such temperatures as will deliver 34 to    40, preferably 35 to 39, and optimally 36 to 38° C. at the wound    bed.

Examples of sources of direct or indirect electromagnetic irradiation ofthe irrigant fluid and/or wound exudate at an appropriate wavelengthinclude infrared and/or near infrared from a radiative heater.

In the apparatus the type and materials of the heater will be largelydetermined by its specific function and the wavelengths and intensitiesto be applied to the fluid within the far infrared, mid infrared or nearinfrared spectrum, and its position in the apparatus of the invention.

Examples of suitable wavelengths to apply to the fluid include:

for the far infrared, 4 to 1000 micrometre,

for the mid infrared, 1.4 to 4 micrometre, and

for the near infrared, 0.75 to 1.5 micrometre.

Examples of suitable levels of intensity include those conventionallyused in medical applications and known to the skilled person.

The higher end of these ranges are potentially more suitable forhospital use, where relatively high intensity infrared or near infraredirradiation at relevant wavelengths may be used safely underprofessional supervision.

Such a device may also suitably be one that is capable of pulsed,continuous, variable, and/or automated and/or programmable operation.

Examples include

-   a) a radiative heater that is an incandescent filament lamp, light    or other like structure, which is a source of radiation at relevant    wavelengths to be applied to the fluid, e.g. infrared or near    infrared irradiation. Examples of a) include a heater that is a    small infrared lamp, mounted on an infra-red transparent dressing    backing layer.-   b) a radiative heater that is a high-thermal energy, high-intensity    LED (light emitting diode) or other like structure, which is a    source of radiation at relevant wavelengths to be applied to the    fluid, e.g. infrared or near infrared irradiation.-   c) a radiative heater that is a high-thermal energy, high-intensity    source of radiation at relevant wavelengths to be applied to the    fluid, e.g. infrared or near infrared irradiation.    -   The type and materials of the heater will be largely determined        by its specific function and the wavelengths and intensities to        be applied to the fluid within the spectrum, and its position in        the apparatus of the invention.-   d) Any r.f. and/or microwave frequency signal generator may be used    provided temperatures at the wound do not exceed 38 to 40° C., and    optimally 36 to 38° C.    -   Examples of sources of direct or indirect electromagnetic        irradiation of the irrigant fluid and/or wound exudate at an        appropriate wavelength also include radio-frequency e.m.r. in a        range of 3 to 300 MHz, such as 10 to 100 MHz, such as 20 to 50        MHz.    -   Examples of preferred frequencies include microwave frequencies,        using a microwave magnetron, in a range such as 1 to 300 GHz,        such as 1 to 100 GHz, e.g. 1 to 50 GHz.    -   It will be appreciated that at these frequencies, in the range        of microwave frequencies in particular, thermal energy is not        just transferred to the fluid by simply being absorbed by the        fluid and conducted to the wound. It is induced in the molecules        in the fluid in the wound by radiation at an optimum frequency        for such materials.    -   In all the above radiative heaters of the irrigant fluid and/or        wound exudate, the electromagnetic irradiation from a radiative        heater may pass into the fluid in the flow path directly,        usually through a ‘window’ that is transparent to the relevant        wavelengths to be applied to the fluid.    -   Amongst those materials that are suitable are glass; carbon        fibres (which may be in a parallel array with spaces        therebetween) and carbon fabric, such as a woven layer or sheet.    -   These may as appropriate be made essentially of carbonised        acrylate, such as polyacrylonitrile and copolymers thereof; and        various well-known polymers.    -   The transmissive structures may, alternatively or additionally,        effectively be in the form of optical fibre(s) or waveguides of        conventional type, e.g.    -   a) a tube, pipe, duct, fibre, filament, strand or other like        structure, e.g. of carbon or the materials mentioned above,        which is transparent to the relevant wavelengths to be applied        to the fluid,    -   b) coated, enclosed or enveloped by a coating, layer, sheet,        skin or concentric tube, pipe, duct, sheath, or casing, or other        like structure, of material on its outer face that is opaque and        reflective to the relevant wavelengths.    -   These may pass at any relevant position along the apparatus flow        path into the apparatus flow path where the heat is desired to        be applied.    -   In one embodiment, they will pass under and/or through the        backing layer of the dressing.    -   The transmissive structures may effectively be in the form of        optical fibre(s) formed by    -   a) at least one inlet pipe and/or fluid supply tube and/or at        least one outlet pipe and/or fluid offtake tube, which passes        through and/or under the wound-facing face, and is transparent        or translucent to the relevant wavelengths to be applied to the        fluid in the wound, and preferably to those that are optimum for        wound healing,    -   b) coated, enclosed or enveloped by a coating, layer, sheet,        skin or concentric tube, pipe, duct, sheath, or casing, or other        like structure, of material on its outer face that is opaque and        reflective to the relevant wavelengths.    -   An advantage of such wound dressings is that these optical        fibres may also serve as diagnostic ‘keyholes’ into the dressing        to the wound bed in order to inspect the wound and assess its        status. This is a significant advantage, in particular in        chronic wounds.    -   As noted above, radiative energy may be absorbed by a component        of the apparatus flow path that absorbs electromagnetic        irradiation at an appropriate wavelength, e.g. infrared and/or        near infrared and is in direct conductive contact with the        irrigant and/or wound exudate.    -   Thus a radiative heater may be radiatively connected to a        component of the apparatus flow path that absorbs        electromagnetic irradiation at an appropriate wavelength, e.g.        infrared and/or near infrared and is in direct conductive        contact with the irrigant and/or wound exudate, e.g. by an air        gap, the component containing a suitable absorbent and        transmissive structure, e.g. an aqueous fluid, such as a        hydrogel, that conducts heat through it to the irrigant fluid.

The temperature of the wound is generally held within a range oftemperatures such as 34 to 40, preferably 35 to 39, and optimally 36 to38° C. at the wound bed.

However, this may not provide a system for optimum performance of thewound healing process. It may be desirable, in particular in chronicwound dialysis, with relatively high concentrations of materials thatare deleterious to wound healing, that the interior of the wounddressing is more beneficially maintained at a temperature that degradessuch molecules in the fluid in the wound, e.g. at appropriate optimumdegradation temperatures for such materials, rather than at normothermictemperature.

Other molecules involved in wound processes that are detrimental towound healing include or gaseous or volatile by-products, such as carbondioxide.

The irrigant may be warmed to a temperature that tends to degrade and/oroutgas such molecules. The degradation or outgassing temperature of eachdetrimental gas, such as carbon dioxide, in aqueous media is eitherknown or may readily be calculated.

Accordingly, another type of this apparatus of the invention forirrigating, supplying thermal energy to and cleansing wounds is providedwith means for maintaining the wound at or near a temperature that isdeleterious to molecules that are detrimental to wound healing.

As noted above, other physiologically active components of the woundcells are beneficial in promoting wound healing and may be stimulated byradiation on the wound under the backing layer.

Where these are enzymes, growth factors and anti-inflammatories, cellmitochondria and other physiologically active components of the exudatefrom a wound, examples of suitable wavelengths and intensities to applyto the fluid in the wound to favour such materials an cell componentswill be known to the skilled person.

As regards the apparatus flowpath, the means for flow switching betweensupply and recirculation may take any form that enables the woundsimultaneously to be

-   -   a) put into communication with the fluid reservoir but    -   b) closed to the fluid recirculation tube, and    -   c) vice versa.

Thus, if there is only one inlet pipe that passes through and/or underthe wound-facing face of the wound dressing, the fluid reservoir isconnected by the fluid supply tube to the flow path via means for flowswitching as desired the into a fluid recirculation tube or a fluidofftake tube.

In this case, the means for flow switching between supply andrecirculation may be a regulator, such as a T-valve.

This is connected in turn to two parts of a fluid recirculation tube ora fluid offtake tube and the fluid supply tube, such that the desiredflow switching between supply and recirculation is achieved.

If there are two or more inlet pipes, these may be connectedrespectively to a fluid supply tube or fluid recirculation tube,respectively having a first regulator and a second regulator, such as avalve or other control device for admitting fluids into the wound.

The desired flow switching between supply and recirculation is achievedby respectively having the first regulator open when the secondregulator is shut, and vice versa.

The means for bleeding the flowpath may be situated in any appropriatepart of the apparatus that is in contact with the irrigant and/or woundexudate, but is usually within the offtake and/or recirculation tubes.

However, it is often as far downstream of and away from the reservoirand the fluid supply tube as possible, so that it may be used to primethe whole of the flowpath from the fluid reservoir via the fluid supplytube.

It may be a regulator, such as a valve or other control device, e.g. aT-valve that is turned to switch between bleed and recirculation, forbleeding fluids from the apparatus, e.g. to a waste reservoir, such as acollection bag.

Alternatively, flow switching between supply and recirculation may notbe desired, but rather concomitant bleeding and/or recirculation isdesired.

The latter may occur when the volume of irrigant and/or wound exudate inrecirculation is increased by continuing addition to it of

-   a) wound exudate, and/or-   b) fluid passing from a cleansing fluid through a selectively    permeable integer, for example in a system such as a dialysis unit.

The means for bleeding the offtake and/or recirculation tubes may thenbe provided in the form of a regulator, such as a simple valve or othercontrol device for admitting or blocking the passage of irrigant and/orexudate through a bleed line branching from the recirculation path.

The means for fluid cleansing may as desired be a ‘single-phase system’.

In this, the circulating fluid from the wound and the fluid reservoirpasses through a self-contained system in which materials deleterious towound healing are removed and the cleansed fluid, still containingmaterials that are beneficial in promoting wound healing, is returnedvia the recirculation tube to the wound bed. Such systems are describedin further detail hereinafter in connection with the means for fluidcleansing.

Alternatively, where appropriate it may be provided in the form of atwo-phase system, such as a dialysis unit, or a biphasic liquidextraction unit.

In this, the circulating fluid from the wound and the fluid reservoirpasses through a system in which the fluid recirculates in indirect or(less usually, direct) contact with a second fluid (dialysate) phase,more usually a liquid.

Materials deleterious to wound healing are removed into the secondphase, and the cleansed fluid, still containing materials that arebeneficial in promoting wound healing, is returned via the recirculationtube to the wound bed. Such systems are described in further detailhereinafter in connection with the means for fluid cleansing.

In use, typically, the means for flow switching between supply andrecirculation tubes is set to admit fluid into the wound from the fluidreservoir but to close the wound to the fluid recirculation tube.

Then, any means for bleeding the offtake and/or recirculation tubes areis opened and the device for moving fluid through the wound and meansfor fluid cleansing is started.

The capacity of the apparatus flow path and the flow rate of irrigantand/or wound exudate from the wound will largely determine whether it isappropriate to run the device to prime the apparatus throughout thewhole length of the apparatus flow path, i.e. to displace any existingfluid reservoir (often air) from the fluid recirculation path, and forhow long it should be run.

Typically, there is a preponderance of irrigant from the fluid reservoirover wound exudate in recirculation, so that use of the device formoving fluid through the wound is appropriate for this purpose.

It is allowed to run until the apparatus is primed throughout the wholelength of the apparatus flow path.

Then, typically the means for bleeding the offtake and/or recirculationtubes is closed, and the means for flow switching between supply andrecirculation tubes is set to close the wound to the fluid reservoir butto admit fluid into the wound from the fluid recirculation tube.

If the means for fluid cleansing is a two-phase system, such as adialysis unit, or a biphasic extraction unit, the cleansing fluid istypically set in motion in contact with the surface of the selectivelypermeable integer, for example the polymer film, sheet or membrane. Ofcourse, the cleansing fluid may less usually be static, and then thisstep is omitted.

As noted below in more detail, the volume of irrigant and/or woundexudate from the wound in recirculation may be increased by continuingaddition to it of

-   a) wound exudate, and/or-   b) fluid passing from a cleansing fluid through a selectively    permeable integer, for example the polymer film, sheet or membrane    of a two-phase system, such as an dialysis unit.

Additionally or alternatively, it may be desired to apply a negativepressure to the wound by means of a device for moving fluid through thewound and means for fluid cleansing applied to the fluid inrecirculation in the fluid recirculation tube downstream of and awayfrom the wound dressing.

In such case, it may be desirable to provide a system in whichconcomitant bleeding and/or recirculation is possible, and to make thenecessary adjustments to maintain the desired balance of fluid inrecirculation by means of the means for bleeding the offtake and/orrecirculation tubes.

The volume of irrigant and/or wound exudate from the wound inrecirculation may be decreased by continuing loss from it of fluidpassing from a cleansing fluid through a selectively permeable integer,for example in a system such as a dialysis unit.

Additionally or alternatively, it may be desired to apply a positivepressure to the wound by means of a device for moving fluid through thewound and means for fluid cleansing applied to the fluid inrecirculation in the fluid recirculation tube upstream of and towardsthe wound dressing.

The means for flow switching between supply and recirculation may besimilarly provided in a form in which concomitant supply and/orrecirculation is possible, and to make the necessary adjustments tomaintain the desired balance of fluid in recirculation by means of themeans for flow switching.

It will be appreciated that where a positive or negative pressure is tobe applied to the wound, at least one hollow body in the recirculationflow path to and from the wound bed should have sufficient resilienceagainst the pressure to allow any significant compression ordecompression of the irrigant fluid to occur.

In all embodiments of the apparatus, the type and material of suchbodies (which are defined by a film, sheet or membrane) that aredescribed by way of example herein to be suitable for use in the presentinvention will be largely capable of this function.

Thus, examples of suitable materials for bodies defined by a film, sheetor membrane, such as inlet or offtake and/or recirculation tubes andstructures such as bags, chambers and pouches, filled with irrigantfluid, e.g. the backing layer of the wound dressing are suitablyelastically resilient thermoplastic materials that are potentiallycapable of this function when pressure is applied in this way.

The present invention in this aspect provides several advantages.

One is that application of a positive pressure to the wound under thebacking layer may make it possible to flood the tissue underlying thewound with one or more physiologically active components.

This may be effected in therapeutically active amounts, to promotegreater wound healing than by treatment with the fluid physiologicallyactive component(s) alone.

Such physiologically active components of the exudate that arebeneficial to wound healing may be e.g. be enzymes or other species andmay be supplied from the dialysate of a dialytic means for fluidcleansing.

It is believed that using the apparatus for irrigating, supplyingthermal energy to and/or cleansing wounds of the present inventioncyclically the effects may be further enhanced.

Such cyclical regimens for such further enhancement may be applied to

-   a) the flow direction, rate, positive or negative pressure,-   b) nature of the circulating fluid (such as water, saline, etc.)    and/or-   c) the thermal energy applied to the wound bed over an extended    period.

Circulating wound fluid aids in movement of biological signallingmolecules involved in wound healing to locations in the wound bed thatare favourable to the wound healing process and/or to cells that wouldotherwise not be exposed to them, e.g. in a highly exuding wound.

This is especially the case in those embodiments of the apparatus ofthis first aspect of the present invention for irrigating, supplyingthermal energy to and/or cleansing wounds where there is an inlet oroutlet manifold from which tubules radiate and run to the wound bed toend in openings that deliver and collect the fluid directly from thewound bed over an extended area.

Such materials include cytokines, enzymes, nutrients for wound cells toaid proliferation, oxygen, and other molecules that are beneficiallyinvolved in wound healing, such as growth factors, and others havingbeneficial effects (which may be further enhanced) in causingchemotaxis.

In all embodiments of the apparatus of this first aspect of the presentinvention for irrigating, supplying thermal energy to and/or cleansingwounds, a particular advantage is the tendency of the wound dressing toconform to the shape of the bodily part to which it is applied.

The wound dressing comprises a backing layer with a wound-facing facewhich is capable of forming a relatively fluid-tight seal or closureover a wound and at least one inlet pipe for connection to a fluidsupply tube or recirculation tube, which passes through and/or under thewound-facing face, and

and at least one outlet pipe for connection to a fluid offtake tube,which passes through and/or under the wound-facing face,

the point at which the or each inlet pipe and the or each outlet pipepasses through and/or under the wound-facing face forming a relativelyfluid-tight seal or closure.

The term ‘relatively fluid-tight seal or closure’ is used herein toindicate one which is fluid- and microbe-impermeable and permits apositive or negative pressure of up to 50% atm., more usually up to 15%atm. to be applied to the wound. The term ‘fluid’ is used herein toinclude gels, e.g. thick exudate, liquids, e.g. water, and gases, suchas air, nitrogen, etc.

The shape of the backing layer that is applied may be any that isappropriate to irrigating, supplying thermal energy to and/or cleansingthe wound across the area of the wound.

Examples of such include a substantially flat film, sheet or membrane,or a bag, chamber, pouch or other structure of the backing layer, e.g.of polymer film, which can contain the fluid.

The backing layer may be a film, sheet or membrane, often with a(generally uniform) thickness of up to 100 micron, preferably up to 50micron, more preferably up to 25 micron, and of 10 micron minimumthickness.

Its largest cross-dimension may be up to 500 mm (for example for largetorso wounds), up to 100 mm (for example for axillary and inguinalwounds), and up to 200 mm for limb wounds (for example for chronicwounds, such as venous leg ulcers and diabetic foot ulcers.

Desirably the dressing is resiliently deformable, since this may resultin increased patient comfort, and lessen the risk of inflammation of awound.

Suitable materials for it include synthetic polymeric materials that donot absorb aqueous fluids, such as

polyolefins, such as polyethylene e.g. high-density polyethylene,polypropylene, copolymers thereof, for example with vinyl acetate andpolyvinyl alcohol, and mixtures thereof;

polysiloxanes;

polyesters, such as polycarbonates;

polyamides, e.g. Nylon 6-6 and 6-10, and

hydrophobic polyurethanes.

They may be hydrophilic, and thus also include hydrophilicpolyurethanes.

They also include thermoplastic elastomers and elastomer blends, forexample copolymers, such as ethyl vinyl acetate, optionally or asnecessary blended with high-impact polystyrene.

They further include elastomeric polyurethane, particularly polyurethaneformed by solution casting.

Preferred materials for the present wound dressing include thermoplasticelastomers and curable systems.

The backing layer is capable of forming a relatively fluid-tight seal orclosure over the wound and/or around the inlet and outlet pipe(s).

However, in particular around the periphery of the wound dressing,outside the relatively fluid-tight seal, it is preferably of a materialthat has a high moisture vapour permeability, to prevent maceration ofthe skin around the wound.

It may also be a switchable material that has a higher moisture vapourpermeability when in contact with liquids, e.g. water, blood or woundexudate. This may, e.g. be a material that is used in Smith & Nephew'sAllevyn™, IV3000™ and OpSite™ dressings.

The periphery of the wound-facing face of the backing layer may bear anadhesive film, for example, to attach it to the skin around the wound.

This may, e.g. be a pressure-sensitive adhesive, if that is sufficientto hold the wound dressing in place in a fluid-tight seal around theperiphery of the wound-facing face of the wound dressing.

Alternatively or additionally, where appropriate a light switchableadhesive could be used to secure the dressing in place to preventleakage. (A light switchable adhesive is one the adhesion of which isreduced by photocuring. Its use can be beneficial in reducing the traumaof removal of the dressing.)

Thus, the backing layer may have a flange or lip extending around theproximal face of the backing layer, of a transparent or translucentmaterial (for which it will be understood that materials that are listedabove are amongst those that are suitable).

This bears a film of a light switchable adhesive to secure the dressingin place to prevent leakage on its proximal face, and a layer of opaquematerial on its distal face.

To remove the dressing and not cause excessive trauma in removal of thedressing, the layer of opaque material on the distal face of the flangeor lip extending around the proximal wound is removed prior toapplication of radiation of an appropriate wavelength to the flange orlip.

If the periphery of the wound dressing, outside the relativelyfluid-tight seal, that bears an adhesive film to attach it to the skinaround the wound, is of a material that has a high moisture vapourpermeability or is a switchable material, then the adhesive film, ifcontinuous, should also have a high or switchable moisture vapourpermeability, e.g. be an adhesive such as used in Smith & Nephew'sAllevyn™, IV3000™ and OpSite™ dressings.

Where a vacuum, is applied to hold the wound dressing in place in afluid-tight seal around the periphery of the wound-facing face of thewound dressing, the wound dressing may be provided with a siliconeflange or lip to seal the dressing around the wound. This removes theneed for adhesives and associated trauma to the patient's skin.

Where the interior of, and the flow of irrigant and/or wound exudate toand through, the dressing is under any significant positive pressure,which will tend to act at peripheral points to lift and remove thedressing off the skin around the wound.

In such use of the apparatus, it may thus be necessary to provide meansfor forming and maintaining such a seal or closure over the woundagainst such positive pressure on the wound, to act at peripheral pointsfor this purpose.

Examples of such means include light switchable adhesives, as above, tosecure the dressing in place to prevent leakage.

Since the adhesion of a light switchable adhesive is reduced byphotocuring, thereby reducing the trauma of removal of the dressing, afilm of a more aggressive adhesive may be used, e.g. on a flange, asabove.

Examples of suitable fluid adhesives for use in more extreme conditionswhere trauma to the patient's skin is tolerable include ones thatconsist essentially of cyanoacrylate and like tissue adhesives, appliedaround the edges of the wound and/or the proximal face of the backinglayer of the wound dressing, e.g. on a flange or lip.

Further suitable examples of such means include

adhesive (e.g. with pressure-sensitive adhesive) and non-adhesive, andelastic and non-elastic straps, bands, loops, strips, ties, bandages,e.g. compression bandages, sheets, covers, sleeves, jackets, sheathes,wraps,

stockings and hose, e.g. elastic tubular hose or elastic tubularstockings that are a compressive fit over a limb wound to apply suitablepressure to it when the therapy is applied in this way; and

inflatable cuffs, sleeves, jackets, trousers, sheathes, wraps, stockingsand hose that are a compressive fit over a limb wound to apply suitablepressure to it when the therapy is applied in this way.

Such means may each be laid out over the wound dressing to extend beyondthe periphery of the backing layer of the wound dressing, and asappropriate will be adhered or otherwise secured to the skin around thewound and/or itself and as appropriate will apply compression (e.g. withelastic bandages, stockings) to a degree that is sufficient to hold thewound dressing in place in a fluid-tight seal around the periphery ofthe wound.

Such means may each be integral with the other components of thedressing, in particular the backing layer.

Alternatively, it may be permanently attached or releasably attached tothe dressing, in particular the backing layer, with an adhesive film,for example, or these components may be a Velcro™, push snap ortwist-lock fit with each other.

The means and the dressing may be separate structures, permanentlyunattached to each other.

In a more suitable layout for higher positive pressures on the wound, astiff flange or lip extends around the periphery of the proximal face ofthe backing layer of the wound dressing as hereinbefore defined.

The flange or lip is concave on its proximal face to define a peripheralchannel or conduit.

It has a suction outlet that passes through the flange or lip tocommunicate with the channel or conduit and may be connected to a devicefor applying a vacuum, such as a pump or a piped supply of vacuum.

The backing layer may be integral with or attached, for example byheat-sealing, to the flange or lip extending around its proximal face.

To form the relatively fluid-tight seal or closure over a wound that isneeded and to prevent passage of irrigant and/or exudate under theperiphery of the wound-facing face of the wound dressing, in use of theapparatus, the dressing is set on the skin around the wound.

The device then applies a vacuum to the interior of the flange or lip,thus forming and maintaining a seal or closure acting at peripheralpoints around the wound against the positive pressure on the wound.

With all the foregoing means of attachment, and means for forming andmaintaining a seal or closure over the wound, against positive ornegative pressure on the wound at peripheral points around the wound,the wound dressing sealing periphery is preferably of a generally roundshape, such as an ellipse, and in particular circular.

To form the relatively fluid-tight seal or closure over a wound andaround the inlet pipe(s) and outlet pipe(s) at the point at which theypass through and/or under the wound-facing face, the backing layer maybe integral with these other components.

The components may alternatively just be a push, snap or twist-lock fitwith each other, or adhered or heat-sealed together.

The or each inlet pipe or outlet pipe may be in the form of an aperture,such as a funnel, hole, opening, orifice, luer, slot or port forconnection as a female member respectively to a mating end of

a fluid recirculation tube and/or fluid supply tube (optionally or asnecessary via means for forming a tube, pipe or hose, or nozzle, hole,opening, orifice, luer, slot or port for connection as a male memberrespectively to a mating end of

a fluid recirculation tube and/or fluid supply tube (optionally or asnecessary via means for flow switching between supply and recirculation)or

a fluid offtake tube.

Where the components are integral they will usually be made of the samematerial (for which it will be understood that materials that are listedabove are amongst those that are suitable).

Where, alternatively, they are a push, snap or twist-lock fit, the maybe of the same material or of different materials. In either case,materials that are listed above are amongst those that are suitable forall the components.

The or each pipe will generally pass through, rather than under thebacking layer.

In such case, the backing layer may often have a rigid and/orresiliently inflexible or stiff area to resist any substantial playbetween the or each pipe and the or each mating tube, or deformationunder pressure in any direction.

It may often be stiffened, reinforced or otherwise strengthened by aboss projecting distally (outwardly from the wound) around each relevanttube, pipe or hose, or nozzle, hole, opening, orifice, luer, slot orport for connection to a mating end of a fluid recirculation tube and/orfluid supply tube or fluid offtake tube.

Alternatively or additionally, where appropriate the backing layer mayhave a stiff flange or lip extending around the proximal face of thebacking layer to stiffen, reinforce or otherwise strengthen the backinglayer.

The wound dressing may not comprise any integer under the backing layerin the wound in use, other than the ribs or ridges mentioned herein.

However, this may not provide a system to distribute irrigant over asufficient functional surface area to irrigate the wound at a practicalrate. To be suitable for use, in particular in chronic wound dialysis,with relatively high concentrations of materials that are deleterious towound healing, it may be advantageous to provide a system where woundirrigant and/or wound exudate may be distributed more evenly, or pass ina more convoluted path under the dressing over the wound bed.

Accordingly, one form of the dressing is provided with a ‘tree’ form ofpipes, tubes or tubules that radiate from an inlet manifold to the woundbed to end in apertures and deliver the circulating fluid directly tothe wound bed via the apertures. Similarly, there is an outlet manifoldfrom which tubules radiate and run to the wound bed to end in openingsand collect the fluid directly from the wound bed.

The pipes, etc. may radiate regularly or irregularly through the woundin use, respectively from the inlet or outlet manifold, althoughregularly may be preferred. A more suitable layout for deeper wounds isone in which the pipes, etc. radiate hemispherically and concentrically,to the wound bed.

For shallower wounds, examples of suitable forms of such layout of thepipes, etc. include ones in which the pipes, etc. radiate in a flattenedhemiellipsoid and concentrically, to the wound bed.

Other suitable forms of layout of the pipes, etc. include one which havepipes, tubes or tubules extending from the inlet pipe(s) and/or outletpipe(s) at the point at which they pass through and/or under thewound-facing face of the backing layer to run over the wound bed. Thesemay have a blind bore with perforations, apertures, holes, openings,orifices, slits or slots along the pipes, etc.

These pipes, etc. then effectively form an inlet pipe manifold thatdelivers the circulating fluid directly to the wound bed or outlet pipeor collects the fluid directly from the wound respectively.

It does so via the holes, openings, orifices, slits or slots in thetubes, pipes, tubules, etc. over most of the wound bed under the backinglayer.

It may be desirable that the tubes, pipes or tubules are resilientlyflexible, e.g. elastomeric, and preferably soft, structures with goodconformability in the wound and the interior of the wound dressing.

When the therapy is applied in this way, the layout of the tubes, pipes,tubules, etc. may depend on the depth and/or capacity of the wound.

Thus, for shallower wounds, examples of suitable forms of such layout ofthe tubes, pipes, tubules, etc. include ones that consist essentially ofone or more of the tubes, etc in a spiral.

A more suitable layout for deeper wounds when the therapy is applied inthis way may be one that comprises one or more of the tubes, etc in ahelix or spiral helix.

Other suitable layouts for shallower wounds include one which haveblind-bore, perforated inlet pipe or outlet pipe manifolds thatcirculate fluid in the wound when the dressing is in use.

One or both of these may be such a form, the other may be, e.g. one ormore straight blind-bore, perforated radial tubes, pipes or nozzles.

Another suitable layout is one in which

an inlet pipe and/or outlet pipe manifold that delivers the circulatingfluid directly to the wound bed or collects the fluid directly from thewound respectively

via inlet and/or outlet tubes, pipes or tubules,

and the inlet manifold and/or outlet manifold is formed by slots inlayers permanently attached to each other in a stack, and

the inlet and/or outlet tubes, pipes or tubules are formed by aperturesthrough layers permanently attached to each other in a stack.

(In FIG. 10 a there is shown an exploded isometric view of such a stack,which is non-limiting.)

As also mentioned herein, the backing layer that is applied may be anythat is appropriate to the present system of therapy and permits apositive or negative pressure of up to 50% atm., more usually up to 25%atm. to be applied to the wound.

It is thus often a microbe-impermeable film, sheet or membrane, which issubstantially flat, depending on any pressure differential on it.

It often has a (generally uniform) thickness similar to such films orsheets used in conventional wound dressings, i.e. up to 100 micron,preferably up to 50 micron, more preferably up to 25 micron, and of 10micron minimum thickness.

The backing layer may often have a rigid and/or resiliently inflexibleor stiff area to resist any substantial play between other componentsthat are not mutually integral, and may be stiffened, reinforced orotherwise strengthened, e.g. by a projecting boss.

Such a form of dressing would not be very conformable to the wound bed,and may effectively form a chamber, hollow or cavity defined by abacking layer and the wound bed under the backing layer.

It may be desirable that the interior of the wound dressing conform tothe wound bed, even for a wound in a highly exuding state. Accordingly,one form of the dressing is provided with a wound filler under thebacking layer.

This is favourably a resiliently flexible, e.g. elastomeric, andpreferably soft, structure with good conformability to wound shape.

It is urged by its own resilience against the backing layer to applygentle pressure on the wound bed.

The wound filler may be integral with the other components of thedressing, in particular the backing layer.

Alternatively, it may be permanently attached to them/it, with anadhesive film, for example, or by heat-sealing, e.g. to a flange or lipextending from the proximal face, so a not to disrupt the relativelyfluid-tight seal or closure over the wound that is needed.

Less usually, the wound filler is releasably attached to the backinglayer, with an adhesive film, for example, or these components may be apush, snap or twist-lock fit with each other.

The wound filler and the backing layer may be separate structures,permanently unattached to each other.

The wound filler may be or comprise a solid integer, favourably aresiliently flexible, e.g. elastomeric, and preferably soft, structurewith good conformability to wound shape. Examples of suitable forms ofsuch wound fillers are foams formed of a suitable material, e.g. aresilient thermoplastic. Preferred materials for the present wounddressing include reticulated filtration polyurethane foams with smallapertures or pores.

Alternatively or additionally, it may be in the form of, or comprise oneor more conformable hollow bodies defined by a film, sheet or membrane,such as a bag, chamber, pouch or other structure, filled with a fluid orsolid that urges it to the wound shape.

The film, sheet or membrane, often has a (generally uniform) thicknesssimilar to that of films or sheets used in conventional wound dressingbacking layers.

That is, up to 100 micron, preferably up to 50 micron, more preferablyup to 25 micron, and of 10 micron minimum thickness, and is oftenresiliently flexible, e.g. elastomeric, and preferably soft.

Such a filler is often integral with the other components of thedressing, in particular the backing layer, or permanently attached tothem/it, with an adhesive film, for example, or by heat-sealing, e.g. toa flange

Examples of suitable fluids contained in the hollow body or bodiesdefined by a film, sheet or membrane include gases, such as air,nitrogen and argon, more usually air, at a small positive pressure aboveatmospheric; and liquids, such as water, saline.

Examples also include gels, such as silicone gels, or preferablycellulosic gels, for example hydrophilic cross-linked cellulosic gels,such as Intrasite™ cross-linked materials.

Examples also include aerosol foams, where the gaseous phase of theaerosol system is air or an inert gas, such as nitrogen or argon, moreusually air, at a small positive pressure above atmospheric; foams,including set aerosol foams, e.g. CaviCare™ foam, and solidparticulates, such as plastics crumbs.

Of course, if the backing layer is a sufficiently conformable and/ore.g. an upwardly dished sheet, the backing layer may lie under the woundfiller, rather than vice versa.

In this type of layout, in order for the wound filler to urge the wounddressing towards the wound bed, it will usually have to be firmlyadhered or otherwise releasably attached to the skin around the wound.This is especially the case in those embodiments where the wound fillerand the backing layer are separate structures, permanently unattached toeach other.

In such a layout for deeper wounds when the therapy is applied in thisway, the means for such attachment may also form and maintain a seal orclosure over the wound.

Where the filler is over the backing layer, and the fluid inlet pipe(s)and outlet pipe(s) pass through the wound-facing face of the backinglayer, they may run through or around the wound filler over the backinglayer.

One form of the dressing is provided with a wound filler under thebacking layer that is or comprises a resiliently flexible, e.g.elastomeric, and preferably soft, hollow body defined by a film, sheetor membrane, such as a bag, chamber, pouch or other structure, withapertures, holes, openings, orifices, slits or slots, or tubes, pipes,tubules or nozzles. It communicates with at least one inlet or outletpipe through at least one aperture, hole, opening, orifice, slit orslot.

The fluid contained in the hollow body may then be the circulating fluidin the apparatus.

The hollow body or each of the hollow bodies then effectively forms aninlet pipe or outlet pipe manifold that delivers the circulating fluiddirectly to the wound bed or collects the fluid directly from the woundrespectively via the holes, openings, orifices, slits or slots, or thetubes, pipes or hoses, etc. in the film, sheet or membrane.

When the therapy is applied in this way, the type of the filler may alsobe largely determined by the depth and/or capacity of the wound.

Thus, for shallower wounds, examples of suitable wound fillers as acomponent of a wound dressing include ones that consist essentially ofone or more conformable hollow bodies defining an inlet pipe and/oroutlet pipe manifold that delivers the circulating fluid directly to thewound bed or collects the fluid directly from the wound.

A more suitable wound filler for deeper wounds when the therapy isapplied in this way may be one which comprises one or more conformablehollow bodies defined by, for example a polymer film, sheet or membrane.

The latter at least partly surround(s) a solid integer, which mayprovide a system with better rigidity for convenient handling.

The wound filler under the backing layer may effectively form an inletor outlet manifold with a direct connection between the inlet pipe(s)and outlet pipe(s) at the point at which they pass through and/or underthe wound-facing face and the wound bed.

If not, in order for aspiration and/or irrigation of the wound bed tooccur, it is appropriate for one or more bores, channels, conduits,passages, pipes, tubes, tubules and/or spaces, etc. to run from thepoint at which the fluid inlet pipe(s) and outlet pipe(s) pass throughand/or under the wound-facing face of the backing layer through oraround the wound filler under the backing layer.

Less usually, the wound filler is an open-cell foam with pores that mayform such bores, channels, conduits, passages and/or spaces through thewound filler under the backing layer.

Where the filler is or comprises one or more conformable hollow bodiesdefined by, for example a polymer film, sheet or membrane, it may beprovided with means for admitting fluids to the wound bed under thewound dressing.

These may be in the form of pipes, tubes, tubules or nozzles runningfrom the point at which the fluid inlet pipe(s) and outlet pipe(s) passthrough and/or under the wound-facing face of the backing layer throughor around the wound filler under the backing layer.

All of the suitable layouts for shallower wounds that compriseblind-bore, perforated inlet pipe or outlet pipe manifolds thatcirculate fluid in the wound when the dressing is in use, that aredescribed hereinbefore, may be used under a wound filler under thebacking layer.

In brief, suitable layouts include ones where one or both manifolds are

annular or toroidal (regular, e.g. elliptical or circular, orirregular), optionally with blind-bore, perforated radial tubes, pipesor nozzles, branching from the annulus or torus; and/or

in a meandering, tortuous, winding, zigzag, serpentine or boustrophedic(i.e. in the manner of a ploughed furrow) pattern, or

defined by slots in and apertures through layers attached to each otherin a stack.

The inlet and/or outlet tubes, the fluid recirculation tube and thefluid supply tube, etc. may be of conventional type, e.g. of ellipticalor circular cross-section, and may suitably have a uniform cylindricalbore, channel, conduit or passage throughout their length.

Depending on the desired fluid volume flow rate of irrigant and/or woundexudate from the wound, and the desired amount in recirculation,suitably the largest cross-dimension of the bore may be up to 10 mm forlarge torso wounds, and up to 2 mm for limb wounds.

The tube walls should suitably thick enough to withstand any positive ornegative pressure on them.

This is the case in particular if the volume of irrigant and/or woundexudate from the wound in recirculation is increased by continuingaddition to it of wound exudate, and/or fluid passing from a cleansingfluid through a selectively permeable integer, for example the polymerfilm, sheet or membrane of a two-phase system, such as an dialysis unit.However, as noted below with regard to pumps, the prime purpose of suchtubes is to convey fluid irrigant and exudate through the length of theapparatus flow path, rather than to act as pressure vessels. The tubewalls may suitably be at least 25 micron thick.

The bore or any perforations, apertures, holes, openings, orifices,slits or slots along the pipes, etc. or in the hollow body or each ofthe hollow bodies may be of small cross-dimension.

They may then effectively form a macroscopic and/or microscopic filterfor particulates including cell debris and micro-organisms, whilstallowing proteins and nutrients to pass through.

Such tubes, pipes or hoses, etc. through and/or around the filler,whether the latter is a solid integer and/or one or more resilientlyflexible or conformable hollow bodies, are described in further detailhereinbefore in connection with the inlet pipe(s) and outlet pipe(s).

The whole length of the apparatus for irrigating, supplying thermalenergy to and/or cleansing wounds should be microbe-impermeable once thewound dressing is over the wound in use.

It is desirable that the wound dressing and the interior of theapparatus for irrigating, supplying thermal energy to and/or cleansingwounds of the present invention is sterile.

The fluid may be sterilised in the fluid reservoir and/or the rest ofthe system in which the fluid recirculates, including the means forfluid cleansing, by ultraviolet, gamma or electron beam irradiation.This way, in particular reduces or eliminates contact of internalsurfaces and the fluid with any sterilising agent.

Examples of other methods of sterilisation of the fluid also includee.g. the use of

ultrafiltration through microapertures or micropores, e.g. of 0.22 to0.45 micron maximum cross-dimension, to be selectively impermeable tomicrobes; and

fluid antiseptics, such as solutions of chemicals, such as chlorhexidineand povidone iodine; metal ion sources, such as silver salts, e.g.silver nitrate; and hydrogen peroxide;

although the latter involve contact of internal surfaces and the fluidwith the sterilising agent.

It may be desirable that the interior of the wound dressing, the rest ofthe system in which the fluid recirculates, and/or the wound bed, evenfor a wound in a highly exuding state, are kept sterile after the fluidis sterilised in the fluid reservoir, or that at least naturallyoccurring microbial growth is inhibited.

Thus, materials that are potentially or actually beneficial in thisrespect may be added to the irrigant initially, and as desired theamount in recirculation increased by continuing addition.

Examples of such materials include antibacterial agents (some of whichare listed above), and antifungal agents.

Amongst those that are suitable are, for example triclosan, iodine,metronidazole, cetrimide, chlorhexidine acetate, sodium undecylenate,chlorhexidine and iodine.

Buffering agents, such as potassium dihydrogen phosphate/disodiumhydrogen phosphate. may be added to adjust the pH, as may localanalgesics/anaesthetics, such as lidocaine/lignocaine hydrochloride,xylocaine (adrenaline, lidocaine) and/or anti-inflammatories, to reducewound pain or inflammation or pain associated with the dressing.

It is also desirable to provide a system in which physiologically activecomponents of the exudate that are beneficial to wound healing are notremoved before or after the application of fluid cleansing.

Examples include the passive deposition of materials that are beneficialin promoting wound healing, such as proteins, e.g. growth factors.

This may occur at any point at least one inlet or outlet pipe through atleast one aperture, hole, opening, orifice, slit or slot.

The fluid contained in the hollow body may the deposition of materialsthat are beneficial in promoting wound healing, and consequent coating,

-   a) may be added to the irrigant initially, and as desired the amount    in recirculation increased by continuing addition, or-   b) may be used at any point or on any integer in the recirculation    path in direct contact with the fluid, e.g. on the means for fluid    cleansing or any desired tube or pipe.

Examples of coating materials for surfaces over which the circulatingfluid passes include

anticoagulants, such as heparin, and

high surface tension materials, such as PTFE, and polyamides,

which are useful for growth factors, enzymes and other proteins andderivatives.

The apparatus of the invention for irrigating, supplying thermal energyto and/or cleansing wounds is provided with means for admitting fluidsdirectly or indirectly to the wound under the wound dressing in the formof a fluid supply tube to a fluid reservoir.

The fluid reservoir may be of any conventional type, e.g. a tube, bag(such as a bag typically used for blood or blood products, e.g. plasma,or for infusion feeds, e.g. of nutrients), chamber, pouch or otherstructure, e.g. of polymer film, which can contain the irrigant fluid.

The reservoir may be made of a film, sheet or membrane, often with a(generally uniform) thickness similar to that of films or sheets used inconventional wound dressing backing layers, i.e. up to 100 micron,preferably up to 50 micron, more preferably up to 25 micron, and of 10micron minimum thickness, and is often a resiliently flexible, e.g.elastomeric, and preferably soft, hollow body.

In all embodiments of the apparatus the type and material of the tubesthroughout the apparatus of the invention for irrigating, supplyingthermal energy to and/or cleansing wounds and the fluid reservoir willbe largely determined by their function.

To be suitable for use, in particular on chronic timescales, thematerial should be non-toxic and biocompatible, inert to any activecomponents, as appropriate of the irrigant from the fluid reservoirand/or wound exudate in the apparatus flow path, and, in any use of atwo-phase system dialysis unit, of the dialysate that moves into thecirculating fluid in the apparatus.

When in contact with irrigant fluid, it should not allow any significantamounts of extractables to diffuse freely out of it in use of theapparatus.

It should be sterilisable by ultraviolet, gamma or electron beamirradiation and/or with fluid antiseptics, such as solutions ofchemicals, fluid- and microbe-impermeable once in use, and flexible.

Examples of suitable materials for the fluid reservoir include syntheticpolymeric materials, such as polyolefins, such as polyethylene, e.g.high-density polyethylene and polypropylene.

Suitable materials for the present purpose also include copolymersthereof, for example with vinyl acetate and mixtures thereof. Suitablematerials for the present purpose further include medical gradepoly(vinyl chloride).

Notwithstanding such polymeric materials, the fluid reservoir will oftenhave a stiff area to resist any substantial play between it andcomponents that are not mutually integral, such as the fluid supply tubetowards the wound dressing, and may be stiffened, reinforced orotherwise strengthened, e.g. by a projecting boss.

The device for moving fluid through the wound and means for fluidcleansing may be any appropriate for this purpose, and may act at anyappropriate point for this purpose.

It may apply a positive or negative pressure to the wound, although itsprime purpose is to move fluid (irrigant from the fluid reservoir and/orwound exudate through the length of the apparatus flow path, rather thanto apply a positive or negative pressure to the wound.

If applied to the fluid in recirculation in the fluid recirculation tubeupstream of and towards the wound dressing and/or the fluid in the fluidsupply tube towards the wound dressing (optionally or as necessary viameans for flow switching between supply and recirculation), it willusually apply positive pressure (i.e. above-atmospheric pressure) to thewound bed.

Often the means for fluid cleansing is (most appropriately for itspurpose) downstream of the wound dressing, and provides the highestresistance in the flow path. This is especially the case where the meansfor fluid cleansing is a single-phase system, e.g. with ultrafiltrationthrough microapertures or micropores, thus enhancing applied positivepressure to the wound.

Where the device is applied to the fluid in recirculation in the fluidrecirculation tube and/or the fluid in the fluid offtake tube downstreamof and away from the wound dressing, it will usually apply negativepressure (i.e. below-atmospheric pressure or vacuum) to the wound bed.

Again, often the means for fluid cleansing is (most appropriately forits purpose) downstream of the wound dressing, and provides the highestresistance in the flow path, thus enhancing applied negative pressure tothe wound.

The following types of pump may be used as desired:

reciprocating pumps, such as:

-   shuttle pumps—with an oscillating shuttle mechanism to move fluids    at rates from 2 to 50 ml per minute;-   diaphragm pumps—where pulsations of one or two flexible diaphragms    displace liquid while check valves control the direction of the    fluid flow.-   piston pumps—where pistons pump fluids through check valves, in    particular for positive and/or negative pressure on the wound bed;

rotary pumps, such as:

-   centrifugal pumps-   flexible impeller-   pumps—where elastomeric impeller traps fluid between impeller blades    and a moulded housing that sweeps fluid through the pump housing.-   progressing cavity-   pumps—with a cooperating screw rotor and stator, in particular for    higher-viscosity and particulate-filled exudate;-   rotary vane pumps—with rotating vaned disk attached to a drive shaft    moving fluid without pulsation as it spins. The outlet can be    restricted without damaging the pump.-   peristaltic pumps—with peripheral rollers on rotor arms acting on a    flexible fluid circulation tube to urge fluid current flow in the    tube in the direction of the rotor.-   vacuum pumps—with pressure regulators.

The type and/or capacity of the device will be largely determined by

-   -   a) the appropriate or desired fluid volume flow rate of irrigant        and/or wound exudate from the wound, and    -   b) whether it is appropriate or desired to apply a positive or        negative pressure to the wound bed, and the level of such        pressure to the wound bed        for optimum performance of the wound healing process, and by        factors such as portability, power consumption and isolation        from contamination.

Such a device may also suitably be one that is capable of pulsed,continuous, variable, reversible and/or automated and/or programmablefluid movement. It may in particular be a pump of any of these types.

In practice, even from a wound in a highly exuding state, such a rate ofexudate flow is only of the order of up to 75 microlitres/cm²/hr (wherecm² refers to the wound area), and the fluid can be highly mobile (owingto the proteases present).

Exudate levels drop and consistency changes as the wound heals, e.g. toa level for the same wound that equates to 12.5-25 microlitres/cm²/hr.

Where materials deleterious to wound healing are removed by a two-phasesystem (see below.), such as a dialysis unit, fluid is also potentiallylost to the system through the means for fluid cleansing.

This may occur, e.g. through a dialysis polymer film, sheet or membranewhich is also permeable to water, in addition to materials deleteriousto wound healing.

The balance of fluid in recirculation may thus further decrease, but maybe adjusted to minimise this undesired loss in a routine manner asdescribed hereinbefore.

Hence, it will be seen that the circulating fluid from the wound willtypically contain a preponderance of irrigant over wound exudate inrecirculation from the fluid reservoir.

The type and/or capacity of the device will thus be largely determinedin this respect by the appropriate or desired fluid volume flow rate ofirrigant, rather than that of exudate, from the wound.

In practice, the ‘normal’ irrigation rate will be different for eachdressing size, but the rate of flow of total irrigant and/or woundexudate will be of the order of 1 to 10 ml/cm²/24 hour, where the cm²refers to the wound area, e.g. 1 to 5 ml/ cm²/24 hour, such as 1 to 3.5ml hr.

If wound temperatures

-   a) above normothermic temperature are required, e.g. a temperature    at or above 42° C., e.g. for the degradative removal of deleterious    materials, or-   b) below normothermic temperatures are required, e.g. 32° C. to 35°    C., e.g. for decreasing the inflammation of a wound,

the necessary target temperature at the heater outlet may be achieved byadjusting parameters, such as increasing or decreasing the linear flowrate of the irrigant and/or any heat exchanger fluid or the temperatureof the heater in a routine manner known to the skilled person.

It is desirable that the interior of the wound dressing and the rest ofthe system in which the fluid recirculates be flushed cyclically beforeand/or after use in treatment, to cleanse them, and it is convenientthat this is effected by the device for moving fluid through the woundand means for fluid cleansing.

Accordingly, the device may deliver a flush cycle at an irrigation ratesubstantially greater than the ‘normal’ rate; this could typically be upto 650 ml/hr for the largest dressing size. It may be desirabletherefore that the apparatus adjusts the heat energy delivered to thewound in accordance with the selected irrigant/exudate flow rates at anymoment in time.

The volume of irrigant and/or wound exudate in recirculation may varyover a wide range, but will typically be e.g. 1 to 8 l. (for example forlarge torso wounds), 30 to 300 ml (for example for axillary and inguinalwounds), and 200 to 1500 ml for limb wounds when the therapy is appliedin this way.

In practice, suitable pressures are of the order of up to 25% atm suchas up to 10% atm. positive or negative pressure on the wound bed, theapparatus being operated as a closed recirculating system.

The higher end of these ranges are potentially more suitable forhospital use, where relatively high % pressures and/or vacua may be usedsafely under professional supervision.

The lower end is potentially more suitable for home use, whererelatively high % pressures and/or vacua cannot be used safely withoutprofessional supervision, or for field hospital use.

The device may be a peristaltic pump or diaphragm pump, e.g. preferablya small portable diaphragm or peristaltic pump. These are preferredtypes of pump, in order in particular to reduce or eliminate contact ofinternal surfaces and moving parts of the pump with (chronic) woundexudate, and for ease of cleaning.

It may suitably be one that applies positive pressure to the woundand/or the means for fluid cleansing.

A preferred pump when the applied pressure is positive is a peristalticpump, e.g. a small, portable peristaltic pump, mounted upstream of themeans for fluid cleansing.

Where the pump is a peristaltic pump, this may be e.g. an Instech ModelP720 miniature peristaltic pump, with a flow rate: of 0.2-180 ml/hr anda weight of <0.5 k. This is potentially useful for home and fieldhospital use.

The pump may suitably be one that applies negative pressure to the woundand/or the means for fluid cleansing.

A preferred pump when the applied pressure is negative is a diaphragmpump, e.g. a small, portable diaphragm pump, mounted downstream of thedressing or the means for fluid cleansing.

Where the pump is a diaphragm pump, and preferably a small portablediaphragm pump, the one or two flexible diaphragms that displace liquidmay each be, for example a polymer film, sheet or membrane, that isconnected to means for creating the pulsations. This may be provided inany form that is convenient, inter alia as a piezoelectric transducer, acore of a solenoid or a ferromagnetic integer and coil in which thedirection of current flow alternates, a rotary cam and follower, and soon.

The outlet from the dressing passes to the means for fluid cleansing forremoval of materials deleterious to wound healing from wound exudate,and in turn to the fluid recirculation tube(s).

The apparatus of the invention for irrigating, supplying thermal energyto and/or cleansing wounds is provided with means for fluid cleansing,which may be

-   a) a single-phase system, such as an ultrafiltration unit, or a    chemical absorption and/or adsorption unit; or-   b) a two-phase system, such as a dialysis unit, or a biphasic    extraction unit.

In the former, circulating fluid from the wound and the fluid reservoirpasses through a self-contained system in which materials deleterious towound healing are removed and the cleansed fluid, still containingmaterials that are beneficial in promoting wound healing are returned tothe wound.

The single-phase system may be of any conventional type.

Examples of such include an ultrafiltration unit, such as a one in whichthe cleansing integer is a filter for materials deleterious to woundhealing, for example a high throughput, low protein-binding polymerfilm, sheet or membrane which is selectively impermeable to materialsdeleterious to wound healing, which are removed and the cleansed fluid,still containing materials that are beneficial in promoting woundhealing is passed by it.

The membrane may preferably be of a hydrophilic polymeric material, suchas a cellulose acetate-nitrate mixture, polyvinylidene chloride, and,for example hydrophilic polyurethane.

Examples of less preferred materials include hydrophobic materials alsoincluding polyesters, such as polycarbonates, PTFE, and polyamides, e.g.nylon 6-6 and 6-10, and hydrophobic polyurethanes, and quartz and glassfibre.

It has microapertures or micropores, the maximum cross-dimension ofwhich will largely depend on the species that are to be selectivelyremoved in this way and those to which it is to be permeable.

The former may be removed with microapertures or micropores, e.g.typically with a maximum cross-dimension in the range of 20 to 700micron, e.g. 20 to 50 nm (for example for undesired proteins), 50 to 100nm, 100 to 250 nm, 250 to 500 nm and 500 to 700 nm.

The filter integer may be a flat sheet or a membrane of a polymericmaterial in a more convoluted form, e.g. in the form of elongatestructure, such as pipes, tubules, etc.

The system may be a chemical adsorption unit, for example one in which aparticulate, such as a zeolite, or a layer, e.g. of a functionalisedpolymer has sites on its surface that are capable of removing materialsdeleterious to wound healing on passing the circulating fluid from thewound and the fluid reservoir over them.

The materials may be removed, e.g. by destroying or binding thematerials that are deleterious to wound healing, by, for examplechelators and/or ion exchangers, degraders, which may be enzymes.

Examples of such also include less specific chemical adsorption units,for example one in which a physical absorbent, such as activated carbonor a zeolite, has non-specific sites on its surface that are capable ofremoving materials deleterious to wound healing on passing thecirculating fluid from the wound and the fluid reservoir over them.

The cleansing integer, for example the polymer film, sheet or otherchemical adsorption means, etc should of course be capable of removingmaterials deleterious to wound healing at a practical rate for a givencapacity of the apparatus flow path and the flow rate of irrigant.

In the two-phase system, circulating fluid from the wound and the fluidreservoir in indirect or (less usually, direct) contact with a secondfluid (dialysate) phase, more usually a liquid.

Thus, in one form, a biphasic liquid extraction unit, the second fluidphase is (usually) a liquid that is immiscible with the circulatingfluid from the dressing, over a surface of which the circulating fluidpasses in direct contact with the cleansing fluid. Materials deleteriousto wound healing are removed into the dialysate, and the cleansed fluid,still containing materials that are beneficial in promoting woundhealing, is returned via the recirculation tube to the wound bed.

Examples of such means for fluid cleansing include those wherein thesecond fluid (dialysate) phase is perfluorodecalin and like materials

Alternatively, where appropriate it may be provided in a form in whichthe two fluids (recirculation fluid and dialysate) are separated by asignificantly two-dimensional integer, for example a polymer film, sheetor membrane or hollow fibre or filament that is permeable to materialsin the circulating fluid in the apparatus.

Again, materials deleterious to wound healing are removed into thedialysate, and the cleansed fluid, still containing materials that arebeneficial in promoting wound healing, is returned via the recirculationtube to the wound bed.

In either form in which the two-phase system, such as a dialysis unit,is provided, in use typically the dialysate moves past the circulatingfluid in the apparatus in a co- or preferably counter-current direction.

Pumps, such as peristaltic pumps, and/or valves control the direction ofthe two fluid flows.

However, the cleansing fluid may less usually be static, although thismay not provide a system with sufficient (dynamic) surface area toremove materials deleterious to wound healing from wound exudate at apractical rate.

Typical dialysate flow rates in a dialytic means for fluid cleansing inthe present apparatus for irrigating, supplying thermal energy to and/orcleansing wounds are those used in the conventional type of two-phasesystem, such as a dialysis unit for systemic therapy.

The integer may be a film, sheet or membrane, often of the same type,and of the same (generally uniform) thickness, as those used inconventional two-phase system, such as a dialysis unit for systemictherapy.

The film, sheet or membrane may be substantially flat, and depending onany pressure differential across it may require other materials on or init to stiffen, reinforce or otherwise strengthen it.

However, this may not provide a system with sufficient functionalsurface area to remove materials deleterious to wound healing from woundexudate at a practical rate.

The surface area of any such film, sheet or membrane may be suitably beno less than 50 mm², such 100 mm² to 1 m², e.g. 500 to 25000 mm^(2.)

To be suitable for use, in particular in chronic wound dialysis, withrelatively high concentrations of materials that are deleterious towound healing, it may therefore be advantageous to provide a system inwhich the film, sheet or membrane of a polymeric material is in a moreconvoluted form.

This may be in the form of elongate structures, such as pipes, tubeshollow fibres or filaments or tubules of a round cross-section, e.g.elliptical or circular, e.g. in a parallel array with spacestherebetween.

The wound irrigant and/or wound exudate may recirculate through theinside and the cleansing fluid may pass into the spaces between adjacentpipes, tubes or tubules in a co- or preferably counter-currentdirection, or vice versa.

Again, materials deleterious to wound healing are removed into thedialysate, and the cleansed fluid, still containing materials that arebeneficial in promoting wound healing, is returned via the recirculationtube to the wound.

Where the means for fluid cleansing is a two-phase system, e.g. in theform of a dialysis unit, or a biphasic extraction unit, the circulatingfluid from the wound and the fluid reservoir passes across one surfacesof a significantly two-dimensional integer, for example a polymer film,sheet or membrane which is selectively permeable to materialsdeleterious to wound healing.

These are removed by passing a cleansing fluid across the other surfaceof the integer. The integer may be a film, sheet or membrane that isselectively permeable to the foregoing materials deleterious to woundhealing.

These as above include

-   oxidants, such as free radicals, e.g. peroxide and superoxide; iron    II and iron III; all involved in oxidative stress on the wound bed;-   proteases, such as serine proteases, e.g. elastase, trypsin;    chymotrypsin and thrombin; cysteine protease inhibitors; matrix    metalloproteases, e.g. collagenase; and carboxyl (acid) proteases;-   endotoxins, such as lipopolysaccharides;-   redox-sensitive genes that are deleterious to wound healing;-   autoinducer signalling molecules, such as homoserine lactone    derivatives, e.g. oxo-alkyl derivatives;-   inhibitors of angiogenesis such as thrombospondin-1 (TSP-1),    plasminogen activator inhibitor, or angiostatin (plasminogen    fragment)-   pro-inflammatory cytokines such as tumour necrosis factor alpha    (TNFα) and interleukin 1 beta (IL-1β); and-   inflammatories, such as lipopolysaccharides, and e.g. histamine.

Examples of suitable materials for the film, sheet or membrane(typically in the form of conformable hollow bodies defined by the film,sheet or membrane, such as the structures described hereinbefore)include natural and synthetic polymeric materials.

The membrane may be of one or more hydrophilic polymeric materials, suchas a cellulose derivative, e.g. regenerated cellulose, a cellulosemono-, di- or tri-esters, such as cellulose mono-, di- or tri-acetate,benzyl cellulose and Hemophan, and mixtures thereof.

Examples of other materials include hydrophobic materials, such asaromatic polysulphones, polyethersulphones, polyetherether-sulphones,polyketones, polyetherketones and polyetherether-ketones, andsulphonated derivatives thereof, and mixtures thereof.

Examples of other materials include hydrophobic materials, such aspolyesters, such as polycarbonates and polyamides, e.g. Nylon 6-6 and6-10; polyacrylates, including, e.g. poly(methyl methacrylate),polyacrylonitrile and copolymers thereof, for exampleacrylonitrile-sodium metallosulphonate copolymers; and poly(vinylidenechloride).

Suitable materials for the present membranes include thermoplasticpolyolefins, such as polyethylene e.g. high-density polyethylene,polypropylene, copolymers thereof, for example with vinyl acetate andpolyvinyl alcohol, and mixtures thereof.

The dialysis membrane should have a molecular weight cut off (MWCO)chosen to allow selective perfusion of species deleterious to woundhealing that have been targeted for removal from the wound. For example,perfusion of the serine protease elastase (molecular weight 25900Dalton) would require a membrane with MWCO>25900 Dalton. The MWCOthreshold can be varied to suit each application between 1 and 3000000Dalton.

Preferably, the MWCO should be as close as possible to this weight toexclude interference by larger competitor species.

For example, such a membrane with MWCO>25900 Dalton does not allow anysignificant amounts of the antagonist to elastase, alpha-1-antitrypsin(AAT) (molecular weight 54000 Dalton), which occurs naturally in wounds,to diffuse freely out of the wound fluid into the dialysate. Theinhibitor, which is beneficial in promoting chronic wound healing,remains in contact with the wound bed, and can act beneficially on it,whilst the elastase that is deleterious to wound healing is removed.

Such use of the present apparatus is, e.g. favourable to the woundhealing process in chronic wounds, such as diabetic foot ulcers, andespecially decubitus pressure ulcers.

As noted hereinafter, antagonists, for example degrading enzymes, orsequestrating agents for elastase on the dialysate side of the membrane,may be used to enhance the removal of this protease from wound exudate.

Where it is desired to remove several different materials that aredeleterious to wound healing, it may be advantageous to provide a systemof modules in series, each of which removes a different material.

This allows incompatible cleansing materials to be used on the samefluid and/or wound exudates.

Preferably any such system is a conventional automated, programmablesystem which can cleanse the wound irrigant and/or wound exudate withminimal supervision.

As noted above in more detail, fluid passes from a cleansing fluidthrough a selectively permeable integer.

This may be the typical permeable polymer film, sheet or membrane of atwo-phase system, such as a dialysis unit.

Additionally, solutes or disperse phase species will pass from thedialysate into the irrigant and/or wound exudate through the dialysispolymer film, sheet or membrane.

This property may be used to perfuse materials beneficial to woundhealing into the irrigant and/or exudate from a dialysate.

In this less conventional type of infusion feed, a broad spectrum ofspecies will usually pass into the exudate and/or irrigant fluid fromthe dialysate.

These include

-   ionic species, such as bicarbonate;-   vitamins, such as ascorbic acid (vitamin C) and vitamin E, and    stable derivatives thereof, and mixtures thereof; to relieve    oxidative stress on the wound bed;-   pH buffering agents, such as potassium dihydrogen phosphate/disodium    hydrogen phosphate,-   local analgesics/anaesthetics, such as lidocaine/lignocaine    hydrochloride and xylocaine (adrenaline lidocaine) and/or    anti-inflammatories, to reduce wound pain or inflammation or pain    associated with the dressing-   nutrients to aid proliferation of wound cells, such as amino acids,    sugars, low molecular weight tissue building blocks and trace    elements; and other cell culture medium species; and-   gases, such as air, nitrogen, oxygen and/or nitric oxide.

For the purposes of fluid cleansing in the apparatus of the presentinvention, both the single-phase system, such as an ultrafiltrationunit, and two-phase system, such as a dialysis unit, may have captive(non-labile, insoluble and/or immobilised) species such as thefollowing.

These are bound to an insoluble and/or immobilised) substrate overand/or through which the irrigant and/or wound exudate from, the wounddressing passes in turn to the fluid recirculation tube(s):

-   antioxidants and free radical scavengers, such as 3-hydroxytyramine    (dopamine), ascorbic acid (vitamin C), vitamin E and glutathione,    and stable derivatives thereof, and mixtures thereof; to relieve    oxidative stress on the wound bed;-   metal ion chelators and/or ion exchangers, such as transition metal    ion chelators, such as iron III chelators (Fe III is involved in    oxidative stress on the wound bed.), such as desferrioxamine (DFO),    3-hydroxytyramine (dopamine); iron III reductants;-   protease inhibitors, such as TIMPs and alpha 1-antitrypsin (AAT);    serine protease inhibitors, such as 4-(2-aminoethyl)-benzene    sulphonyl fluoride (AEBSF, PefaBloc) and Nα-p-tosyl-L-lysine    chloro-methyl ketone (TLCK) and ε-aminocaproyl-p-chlorobenzylamide;    cysteine protease inhibitors; matrix metalloprotease inhibitors; and    carboxyl (acid) protease inhibitors;-   sacrificial redox materials that are potentially or actually    beneficial in promoting wound healing, by the removal of materials    that trigger the expression into wound exudate of redox-sensitive    genes that are deleterious to wound healing; autoinducer signalling    molecule degraders, which may be enzymes; and-   anti-inflammatory materials to bind or destroy lipopolysaccharides,    e.g. peptidomimetics

Other physiologically active components of the exudate that aredeleterious to wound healing may be removed in this way.

These may be removed with suitable chelators and/or ion exchangers,degraders, which may be enzymes, or other species.

The following types of functionalised substrate has sites on its surfacethat are capable of removing materials deleterious to wound healing onpassing the circulating fluid from the wound and the fluid reservoirover them:

heterogeneous resins, for example silica-supported reagents such as:metal scavengers,

-   3-(diethylenetriamino)propyl-functionalised silica gel-   2-(4-(ethylenediamino)benzene)ethyl-functionalised silica gel-   3-(mercapto)propyl-functionalised silica gel-   3-(1-thioureido)propyl-functionalised silica gel-   triamine tetraacetate-functionalised silica gel    or electrophilic scavengers,-   4-carboxybutyl-functionalised silica gel-   4-ethyl benzenesulfonyl chloride-functionalised silica gel-   propionyl chloride-functionalised silica gel-   3-(isocyano)propyl-functionalised silica gel-   3-(thiocyano)propyl-functionalised silica gel-   3-(2-succinic anhydride)propyl-functionalised silica gel-   3-(maleimido)propyl-functionalised silica gel    or nucleophilic scavengers,-   3-aminopropyl-functionalised silica gel-   3-(ethylenediamino)-functionalised silica gel-   2-(4-(ethylenediamino)propyl-functionalised silica gel-   3-(diethylenetriamino)propyl-functionalised silica gel-   4-ethyl-benzenesulfonamide-functionalised silica gel-   2-(4-toluenesulfonyl hydrazino)ethyl-functionalised silica gel-   3-(mercapto)propyl-functionalised silica gel-   dimethylsiloxy-functionalised silica gel    or base or acid scavengers,-   3-(dimethylamino)propyl-functionalised silica gel-   3-(1,3,4,6,7,8-hexahydro-2H-pyrimido-[1,2-α]pyrimidino)propyl-functionalised    silica gel-   3-(1-imidazol-1-yl)propyl-functionalised silica gel-   3-(1-morpholino)propyl-functionalised silica gel-   3-(1-piperazino)propyl-functionalised silica gel-   3-(1-piperidino)propyl-functionalised silica gel-   3-(4,4′-trimethyldipiperidino)propyl-functionalised silica gel-   2-(2-pyridyl)ethyl-functionalised silica gel-   3-(trimethylammonium)propyl-functionalised silica gel    or the reagents,-   3-(1-cyclohexylcarbodiimido)propyl-functionalised silica gel-   TEMPO-functionalised silica gel-   2-(diphenylphosphino)ethyl-functionalised silica gel-   2-(3,4-cyclohexyldiol)propyl-functionalised silica gel-   3-(glycidoxy)propyl-functionalised silica gel-   2-(3,4-epoxycyclohexyl)propyl-functionalised silica gel-   1-(allyl)methyl-functionalised silica gel-   4-bromopropyl-functionalised silica gel-   4-bromophenyl-functionalised silica gel-   3-chloropropyl-functionalised silica gel-   4-benzyl chloride-functionalised silica gel-   2-(carbomethoxy)propyl-functionalised silica gel-   3-(4-nitrobenzamido)propyl-functionalised silica gel-   3-(ureido)propyl-functionalised silica gel    or any combinations of the above.

The use of such captive (non-labile, insoluble and/or immobilised)species, such as the foregoing, bound to an insoluble and immobilised)substrate over and/or through which the irrigant and/or wound exudatefrom, the wound dressing passes has been described hereinbefore assuitable for the means for fluid cleansing.

However, they may additionally, where appropriate, be used in any partof the apparatus that is in contact with the irrigant and/or woundexudate, but often within the dressing, for removal of materialsdeleterious to wound healing from wound.

A backing layer in the wound dressing with ribs or ridges may be used toassist in channelling fluid across a larger area over a longer dwelltime, and hence improve the cleansing of the irrigant in the wounddressing.

The means for fluid cleansing may additionally, where appropriate,comprise one or more macroscopic and/or microscopic filters.

These are to retain particulates, e.g. cell debris and micro-organisms,allowing proteins and nutrients to pass through.

Alternatively, a less conventional type of two-phase system (see above),such as a dialysis unit, may be used as the means for fluid cleansing.In this type, the dialysis polymer film, sheet or membrane is not aninteger selectively permeable to materials deleterious to wound healing,such as

proteases, such as serine proteases, e.g. elastase, trypsin;chymotrypsin and thrombin; cysteine protease inhibitors; matrixmetalloproteases, e.g. collagenase; and carboxyl (acid) proteases;

endotoxins, such as lipopolysaccharides;

inhibitors of angiogenesis such as thrombospondin-1 (TSP-1), plasminogenactivator inhibitor, or angiostatin (plasminogen fragment);

pro-inflammatory cytokines such as tumour necrosis factor alpha (TNFα)and interleukin 1 beta (IL-1β); and

oxidants, such as free radicals, e.g., e.g. peroxide and superoxide;metal ions, e.g. iron II and iron III; all involved in oxidative stresson the wound bed.

It will however also permit components of the exudate from a woundand/or irrigant fluid that may be larger or smaller molecules, but arebeneficially involved in wound healing to pass into and through it.

In the dialysate, or preferably in one or more solid structural integerswith at least one surface in contact with the dialysate, in the meansfor fluid cleansing, there are one or more materials that can removematerials deleterious to wound healing from wound exudate, by being

antagonists to such species, for example enzymes or others, such as

protease inhibitors, such as serine protease inhibitors, such as4-(2-aminoethyl)-benzene sulphonyl fluoride (AEBSF, PefaBloc) andNα-p-tosyl-L-lysine chloromethyl ketone (TLCK) andε-aminocaproyl-p-chlorobenzylamide; cysteine protease inhibitors; matrixmetalloprotease inhibitors; and carboxyl (acid) protease inhibitors;

peroxide inhibitors, such as catalase;

binders and/or degraders, such as anti-inflammatory materials to bind ordestroy lipopolysaccharides, e.g. peptidomimetics;

anti-oxidants, such as 3-hydroxytyramine (dopamine), ascorbic acid(vitamin C), vitamin E and glutathione, and stable derivatives thereof,and mixtures thereof; to relieve oxidative stress on the wound bed; and

chelators and/or ion exchanges, such as desferrioxamine (DFO),3-hydroxytyramine (dopamine).

They further include peptides (including cytokines, e.g. bacterialcytokines, such as α-amino-γ-butyrolactone and L-homocarnosine); and

sacrificial redox materials that are potentially or actually beneficialin promoting wound healing, such as iron III reductants; and/or removematerials that trigger the expression into wound exudate ofredox-sensitive genes, by degrading them; and

other physiologically active components.

In use of the two-phase system dialysis unit, of this less conventionaltype, a broad spectrum of species will usually pass into the dialysatefrom the exudate.

Some (mainly ionic) species will pass from the dialysate into theirrigant and/or wound exudate through the dialysis polymer film, sheetor membrane that is not very selectively permeable to materialsdeleterious to wound healing.

The components of the exudate from a wound and/or irrigant fluid willdiffuse freely to and fro through it.

If (preferably) none of the dialysate is voided to waste, e.g. to acollection bag, a steady state concentration equilibrium is eventuallyset up between the dialysate and the irrigant and/or wound exudate,which is ‘topped up’ from the wound dressing.

Circulating wound fluid aids in the quicker attainment of thisequilibrium of materials beneficial in promoting wound healing.

It also returns them to the site where they can be potentially of mostbenefit, i.e. the wound bed.

The target materials deleterious to wound healing also pass into thedialysate from the exudate through the dialysis polymer film, sheet ormembrane that is not very selectively permeable to materials deleteriousto wound healing.

Unlike the other components of the exudate from a wound and/or irrigantfluid, the target materials deleterious to wound healing come intocontact with the dialysate, or preferably with one or more solidstructural integers with at least one surface in the dialysate, and areremoved by the appropriate antagonists, binders and/or degraders,chelators and/or ion exchangers and redox agents, etc.

The cleansed fluid, still containing some materials that are beneficialin promoting wound healing, is returned to the recirculation tube.

Unlike the other components of the exudate from a wound and/or irrigantfluid the target materials are constantly removed from the dialysate,very little of these species will pass from the dialysate, into theirrigant and/or wound exudate, and a steady state concentrationequilibrium is not set up, even if the species are constantly ‘toppedup’ from the wound dressing.

It is believed that circulating wound fluid aids in removal fromrecirculation of the materials deleterious to wound healing from woundexudate, whilst retaining materials that are beneficial in promotingwound healing in contact with the wound.

A particular advantage of this form of the two-phase system is where amaterial that can remove materials deleterious to wound healing fromwound exudate is (cyto)toxic or bioincompatible, or not inert to anycomponents that are beneficial in promoting wound healing.

The system does not allow any significant amounts of antagonist todiffuse freely out of the dialysate into the irrigant fluid. The activematerial can act beneficially on the fluid however.

The film sheet or membrane is preferably a dialysis membrane ofmolecular weight cut off (MWCO) chosen to allow perfusion of speciestargeted for sequestration or destruction.

For example, sequestration of the serine protease elastase (molecularweight 25900 Dalton) would require a membrane with MWCO>25900 Dalton.

The MWCO threshold can be varied to suit each application between 1 and3000000 Dalton. Preferably, the MWCO should be as close as possible tothis weight to exclude sequestering interference by larger competitorspecies.

Both the single-phase system, such as an ultrafiltration unit, andtwo-phase system, such as a dialysis unit, may be in modular form thatis relatively easily demountable from the apparatus of the invention.The system may suitably comprise one or more such modules.

The conduits through which respectively

-   a) the irrigant and/or wound exudate passes from the wound dressing    and-   b) the cleansed fluid, still containing materials that are    beneficial in promoting wound healing, is returned to the    recirculation tube, and-   c) (in the case where the means is provided in the form of a    two-phase system, such as an dialysis unit) through which the    cleansing fluid enters and exits the means

preferably have means for, on module disconnection and withdrawal,

-   i) switching off the flow and-   ii) providing an immediate fluid-tight seal or closure over the ends    of the conduits and the cooperating tubes in the rest of the    apparatus of the invention so exposed,

to prevent continuing passage of irrigant and/or exudate and cleansedfluid, and cleansing fluid.

The apparatus of the invention for irrigating, supplying thermal energyto and/or cleansing wounds is provided with means for bleeding theofftake and/or recirculation tubes, such as a regulator, such as a valveor other control device for bleeding fluids from the wound.

The device for moving fluid through the wound and means for fluidcleansing is used to move irrigant to the wound dressing and apply thedesired positive or negative pressure on the wound bed.

The desired balance of fluid in recirculation tube will typically beregulated by means of

-   a) the means for bleeding the offtake and/or recirculation tubes,-   b) the means for flow switching between supply and recirculation,    and/or-   c) the means for moving fluid over the wound bed and through the    means for fluid cleansing,    as appropriate.

Thus, e.g. if

-   a) the apparatus for irrigating, supplying thermal energy to and/or    cleansing wounds is a single-phase system, such as an    ultrafiltration unit,-   b) the wound is not in a highly exuding state and-   c) it is not appropriate or desired to admit fluid into the wound    from the fluid reservoir,

there is no or negligible change in the balance of fluid inrecirculation.

Once it has been primed throughout, e.g. to the desired positive ornegative pressure on the wound bed, the apparatus may be operated as aclosed recirculating system.

The means for flow switching between supply and recirculation tubes isset to close the wound to the fluid reservoir via the fluid supply tube,and the means for bleeding the offtake and/or recirculation tubes arealso closed.

If

-   a) the apparatus for irrigating, supplying thermal energy to and/or    cleansing wounds is a single-phase system, such as an    ultrafiltration unit,-   b) the wound is in a highly exuding state and/or-   c) it is appropriate or desired to admit fluid into the wound from    the fluid reservoir,    there is a positive change in the balance of fluid in recirculation.

Once it has been primed throughout, e.g. to the desired positive ornegative pressure on the wound bed, the apparatus cannot be operated asa closed recirculating system, without the pressure to the wound bedincreasing, possibly undesirably.

The means for bleeding the offtake and/or recirculation tubes must beopened to some extent to relieve positive pressure on the wound bed. Thebleed-off may be voided to waste, e.g. to a collection bag.

Materials that are beneficial in promoting wound healing may be lost tothe site where they can be potentially of most benefit, i.e. the woundbed, when the therapy is applied in this way.

However, the balance of fluid in recirculation may be routinely adjustedto minimise this undesired loss.

The factors that determine the balance of fluid in recirculation in anapparatus with a two-phase system means for fluid cleansing in the formof a dialysis unit, or a biphasic extraction unit have been described indetail hereinbefore in connection with the operation of the apparatus.It is sufficient to note here that at some point after steady staterecirculation established through the length of the apparatus flow path,it may be necessary that any bleed valve is opened, if overall the fluidlevel is increasing by transfer from the dialysate to an undesirableextent.

Other combinations, and the necessary adjustments to maintain thedesired balance of fluid in recirculation tube by means of

-   a) the means for bleeding the offtake and/or recirculation tubes,-   b) the means for flow switching between supply and recirculation,    and/or-   c) the means for moving fluid    will be apparent to the skilled person.

The outlet from the means for bleeding the offtake and/or recirculationtubes may be collected and monitored and used to diagnose the status ofthe wound and/or its exudate.

The waste reservoir may be of any conventional type, e.g. a tube, bag(such as a bag typically used as an ostomy bag), chamber, pouch or otherstructure, e.g. of polymer film, which can contain the irrigant fluidthat has been bled off. In all embodiments of the apparatus, the typeand material of the waste reservoir will be largely determined by itsfunction. To be suitable for use, the material need only befluid-impermeable once in use, and flexible.

Examples of suitable materials for the fluid reservoir include syntheticpolymeric materials, such as polyolefins, such as poly (vinylidenechloride).

Suitable materials for the present purpose also include polyethylene,e.g. high-density polyethylene, polypropylene, copolymers thereof, forexample with vinyl acetate and mixtures thereof.

In a second aspect of the present invention there is provided aconformable wound dressing, characterised in that it comprises a backinglayer with a wound-facing face which is capable of forming a relativelyfluid-tight seal or closure over a wound and has

-   at least one inlet pipe for connection to a fluid supply tube, which    passes through and/or under the wound-facing face, and-   at least one outlet pipe for connection to a fluid offtake tube,    which passes through and/or under the wound-facing face,-   the point at which the or each inlet pipe and the or each outlet    pipe passes through and/or under the wound-facing face forming a    relatively fluid-tight seal or closure over the wound,-   the dressing having means for supplying thermal energy to the fluid    in the wound.

The dressing is advantageously provided for use in a bacteria-proofpouch. Examples of suitable forms of such wound dressings are asdescribed by way of example hereinbefore.

It is an object of the present invention

-   a) obviate at least some of the disadvantages of known aspiration    and/or irrigation therapies, and-   b) provide a system of therapy which    -   i) can remove materials deleterious to wound healing from wound        exudate, whilst retaining materials that are beneficial in        promoting wound healing in contact with the wound bed, and/or    -   ii) which allows fluids containing active amounts of materials        that are beneficial in promoting wound healing to pass into        and/or through the wound in contact with the wound bed.

Thus, in a third aspect of the present invention there is provided amethod of treating wounds to promote wound healing using the apparatusfor irrigating, supplying thermal energy to and/or cleansing wounds ofthe present invention.

The present invention will now be described by way of example only withreference to the accompanying drawings in which:

FIG. 1 is a schematic view of an apparatus for irrigating, supplyingthermal energy to and/or cleansing a wound according to the first aspectof the present invention.

It has a single-phase system means for fluid cleansing in the form of anultrafiltration unit.

FIG. 2 is a schematic view of an apparatus for irrigating, supplyingthermal energy to and/or cleansing a wound according to the first aspectof the present invention.

It has a two-phase system means for fluid cleansing in the form of adialysis unit, or a biphasic extraction unit.

The means for supplying conducted thermal energy are omitted from theschematics for clarity.

FIGS. 3 to 6 are cross-sectional side views of conformable wounddressings, of the second aspect of the present invention for aspiratingand/or irrigating wounds.

FIG. 7 is a schematic view of an apparatus for aspirating, irrigatingand/or cleansing a wound according to the first aspect of the presentinvention. It has a single-phase system means for fluid cleansing in theform of an ultrafiltration unit.

FIG. 8 is a schematic view of an apparatus for aspirating, irrigatingand/or cleansing a wound according to the first aspect of the presentinvention. It has a two-phase system means for fluid cleansing in theform of a dialysis unit, or a biphasic extraction unit.

FIG. 9 is a schematic view of another apparatus for aspirating,irrigating and/or cleansing a wound according to the first aspect of thepresent invention. It has a single-phase system means for fluidcleansing in the form of an ultrafiltration unit.

Referring to FIG. 1, the apparatus (1) for irrigating, supplying thermalenergy to and/or cleansing wounds comprises

-   a conformable wound dressing (2), having-   a backing layer (3) which is capable of forming a relatively    fluid-tight seal or closure (4) over a wound (5) and-   one inlet pipe (6) for connection to a fluid supply tube (7), which    passes through the wound-facing face of the backing layer (5) at    (8), and-   one outlet pipe (9) for connection to a fluid offtake tube (10),    which passes through the wound-facing face at (11),-   the points (8), (11) at which the inlet pipe and the outlet pipe    passes through and/or under the wound-facing face forming a    relatively fluid-tight seal or closure over the wound, and-   means for supplying conducted thermal energy to the fluid in the    wound in the form of an electrical heater (111) (not shown) on the    inlet pipe (6). (In a variant of this apparatus noted further below,    the means for supplying conducted thermal energy to the fluid in the    wound is in the form of an electrical heat pad mounted on top of the    backing layer (3) which is capable of conducting heat to the wound    (5) through the irrigant.),-   the inlet pipe being connected via means for flow switching between    supply and recirculation, here a T-valve (14), by the fluid supply    tube (7) to a fluid reservoir (12) and to a fluid recirculation tube    (13) having a means for bleeding the tube, here a bleed T-valve (16)    to waste, e.g. to a collection bag (not shown),-   the outlet pipe (9) being connected to a fluid offtake tube (15),    connected in turn to-   means for fluid cleansing (17), here in the form of an    ultrafiltration unit, connected to the inlet pipe (6) via the fluid    recirculation tube (13) and T-valve (14), and-   a device for moving fluid through the wound and means for fluid    cleansing (17), here a peristaltic pump (18), e.g. preferably a    small portable peristaltic pump, acting on the fluid circulation    tube (13) with the peripheral rollers on its rotor (not shown) to    apply a low negative pressure on the wound.

The ultrafiltration unit (17) is a single-phase system.

In this the circulating fluid from the wound and the fluid reservoirpasses through a self-contained system in which materials deleterious towound healing are removed and the cleansed fluid, still containingmaterials that are beneficial in promoting wound healing, is returnedvia the recirculation tube to the wound bed.

(In a variant of this apparatus, there are two inlet pipes (6), whichare connected respectively to a fluid supply tube (7) and fluidrecirculation tube (13), respectively having a first valve (19) foradmitting fluid into the wound from the fluid reservoir (12) and asecond valve (20) for admitting fluid into the wound from therecirculation tube. Usually in use of the apparatus, when the firstvalve (19) is open, the second valve (20) is shut, and vice versa.)

In use of the apparatus (1), the valve (16) is opened to a collectionbag (not shown), and the T-valve (14) is turned to admit fluid from thefluid reservoir to the wound dressing through the fluid supply tube (7)and inlet pipe (6).

(In the variant of this apparatus having two inlet pipes (6), which areconnected respectively to a fluid supply tube (7) and fluidrecirculation tube (13), the first valve (19) for admitting fluid intothe wound from the fluid reservoir (12) is opened and the second valve(20) is shut, and vice versa.)

The pump (18) is started to nip the fluid recirculation tube (13) withthe peripheral rollers on its rotor (not shown) to apply a low positivepressure on the wound. It is allowed to run until the apparatus isprimed throughout the whole length of the apparatus flow path and excessfluid is voided to waste via the bleed T-valve (16) into the collectionbag (not shown).

The electrical heater (111) on inlet pipe (6) is turned on to supplyconducted thermal energy to the fluid in the wound.

The T-valve (14) is then turned to switch from supply and recirculation,i.e. is set to close the wound to the fluid reservoir (12) but to admitfluid into the wound from the fluid recirculation tube (13), and thebleed T-valve (16) is simultaneously closed.

(In the variant of this apparatus, where there are two inlet pipes (6),which are connected respectively to a fluid supply tube (7) and fluidrecirculation tube (13), the first valve (19) is closed and arecirculating system set up by opening the second valve (20) foradmitting fluid into the wound from the recirculation tube (13).

The circulating fluid from the wound and the fluid reservoir (12) passesthrough the ultrafiltration unit (17). Materials deleterious to woundhealing are removed and the cleansed fluid still containing materialsthat are beneficial in promoting wound healing, is returned via therecirculation tube (13) to the wound bed.

The recirculation of fluid may be continued as long as desired.

Switching between supply and recirculation is then reversed, by turningthe T-valve (14) to admit fluid from the fluid reservoir to the wounddressing through the fluid supply tube (7) and inlet pipe (6).

(In the variant of this apparatus having two inlet pipes (6), which areconnected respectively to a fluid supply tube (7) and fluidrecirculation tube (13), the first valve (19) for admitting fluid intothe wound from the fluid reservoir (12) is opened and the second valve(20) is shut, and vice versa.)

The bleed valve (16) is simultaneously opened, so that fresh fluidflushes the recirculating system.

The running of the pump (18) may be continued until the apparatus isflushed, when it and the fluid recirculation is stopped, and theelectrical heater (111) on inlet pipe (6) is turned off.

If, e.g. the wound is in a highly exuding state, there is a positivechange in the balance of fluid in recirculation. It may be necessary tobleed fluid from recirculation, by opening the bleed T-valve (16) tobleed fluid from the recirculation tube (13).

Referring to FIG. 2, the apparatus (21) is a variant of that of FIG. 1,with identical, and identically numbered, components, except for themeans for fluid cleansing, which is in the form of a two-phase system,here a dialysis unit (23).

In this, there is one system through which the circulating fluid fromthe wound and the fluid reservoir passes and from which deleteriousmaterials are removed by selectively permeable contact with a secondsystem, through which passes a cleansing fluid.

The dialysis unit (23) thus has an internal polymer film, sheet ormembrane (24), selectively permeable to materials deleterious to woundhealing, which divides it into

-   a) a first chamber (25), through which passes a cleansing fluid    across one surface of the polymer film, sheet or membrane, and-   b) a second chamber (26), through which passes the circulating fluid    from the wound and the fluid reservoir (12), and from which    deleterious materials are removed

The dialysis unit (23) thus has a dialysate inlet pipe (28) connectingto a dialysate supply tube (29) which passes to a peristaltic pump (38),e.g. preferably a small portable peristaltic pump, acting on thedialysate supply tube (29) with the peripheral rollers on its rotor (notshown) to supply cleansing fluid across the surface of the polymer film,sheet or membrane (28) in the first chamber (25) from a dialysatereservoir (not shown) via a valve (34).

The dialysis unit (23) also has a dialysate outlet pipe (30) connectingto a dialysate outlet tube (31) which passes to waste via a second bleedT-valve (36) into, e.g. a collection bag (not shown).

Operation of this apparatus is similar to that of FIG. 1, except for thedialysis unit (23), in that at some point after the irrigation system isprimed and steady state recirculation established through the length ofthe apparatus flow path, the valve (34) and second bleed valve (36) areopened.

The pump (38) is started to nip fluid dialysate tube (29) with theperipheral rollers on its rotor (not shown) to pump cleansing fluid tothe first chamber from a dialysate reservoir (not shown) and out towaste via the bleed valve (36) into the collection bag (not shown).

The dialysis unit (23) is a module (or scrubbing cartridge) with asubstrate that changes colour to indicate the presence of detrimentalfactors in the cleansed fluid, and that the scrubbing cartridge isexhausted and should be renewed.

Referring to FIGS. 3 to 7, each dressing (41) is in the form of aconformable body defined by a microbe-impermeable film backing layer(42) with a uniform thickness of 25 micron, with a wound-facing face(43) which is capable of forming a relatively fluid-tight seal orclosure over a wound.

The backing layer (42) extends in use on a wound over the skin aroundthe wound. On the proximal face of the backing layer (43) on the overlap(44), it bears an adhesive film (45), to attach it to the skinsufficiently to hold the wound dressing in place in a fluid-tight sealaround the periphery of the wound-facing face (43) of the wounddressing.

There is one inlet pipe (46) for connection to a fluid supply tube (notshown), which passes through and/or under the wound-facing face (43),and one outlet pipe (47) for connection to a fluid offtake tube (notshown), which passes through and/or under the wound-facing face (43),

Referring to FIG. 3, one form of the dressing comprises a circular sheet(70) that lies under a circular backing layer (72) and is permanentlyattached to a boss (81), which is e.g. heat-sealed to the backing layer(72).

An annular layer of foam (74) formed of a suitable material, e.g. aresilient thermoplastic, preferably a reticulated filtrationpolyurethane foam with small apertures or pores, spaces the sheet (70)from the backing layer and surrounds the boss (81).

A downwardly dished membrane (75) with openings (76) is permanentlyattached to the sheet (70) by heat-sealing to form a chamber (77) withthe sheet (70).

An inlet pipe (76) and outlet pipe (77) are mounted centrally in theboss (81) and pass through the backing layer (72).

The inlet pipe (76) is made of a polyurethane tubular core (not shown)surrounded by an annulus of resistive conductive material, such as oneof the resistive alloys noted hereinbefore, which generates thermalenergy when a voltage drop is applied over it. It is connected to a cell(78), shown schematically, which applies a voltage drop over it.

The inlet pipe (76) communicates with the interior of the chamber (77),which thus forms an inlet manifold that distributes heated fluiddirectly to the wound when the dressing is in use.

The outlet pipe (77) extends radially immediately under the backinglayer (3) and communicates with the inner face of the layer of foam(74), which forms an outlet manifold.

This form of the dressing is a more suitable layout for shallow wounds

Another form of dressing is shown in FIG. 4. An inlet pipe (76) andoutlet pipe (77) are mounted centrally in a boss (81) in, and passthrough a backing layer (3). An oblately hemispheroidal filler (88) withan annular groove (89) may be permanently attached to the pipes (76) and(77). It is formed of a suitable material, e.g. a resilientthermoplastic foam, preferably a reticulated filtration polyurethanefoams with small apertures or pores.

An annular electrical heat pad (90) is mounted around the boss (81) ontop of the backing layer (3), which is capable of conducting heat to thewound (5) through the irrigant.

It may be in the form of non-woven or woven fabric, such as a wovenlayer or sheet of carbon fibres or a fabric, such as a woven layer orsheet made essentially of carbonised acrylate, such as polyacrylonitrileand copolymers thereof, which generate thermal energy when a voltagedrop is applied over it.

Alternatively, it may be an electrically insulating flat sheet ormembrane substrate that has an electrically resistive but conductiveprinted circuit on it. It is connected to a cell (78), shownschematically, which applies a voltage drop over it.

The inlet pipe (76) communicates with the wound space at the lowestpoint of the filler (88). The outlet pipe (77) communicates with thegroove (89), and effectively collects the fluid from the wound peripherywhen the dressing is in use.

This form of the dressing is a more suitable layout for deeper wounds.

In FIG. 5, an inlet pipe (76) and outlet pipe (77) are mounted centrallyin a boss (81) in, and pass through a backing layer (3).

An oblately spheroidal conformable hollow body (78) is defined by amembrane (79) which is filled with a fluid, here air or nitrogen, thaturges it to the wound shape, and is permanently attached to the pipes(76) and (77). It is formed of a suitable material, e.g. a resilientthermoplastic, preferably a reticulated filtration polyurethane foamwith small apertures or pores.

The inflation inlet pipe (350) communicates with the interior of thehollow body (78), to permit inflation of the body (78). The inlet pipe(76) extends through the hollow body (78). The outlet pipe (77)communicates with an outlet manifold formed by a series of radialapertures in a foam disc (87) immediately under the backing layer, whichcollects the fluid from the wound periphery when the dressing is in use.

An electrical heater (90) is mounted under the boss (81) on top of thebacking layer (3), which is transparent to radiant heat, and so permitits transmission to the wound (5) through the irrigant.

It may be in the form of a near infrared radiant heater that generatesthermal energy when a voltage drop is applied over it. It is connectedto a cell (78), shown schematically, which applies a voltage drop overit.

Referring to FIG. 6 a, another form for deeper wounds is shown. Thiscomprises a circular, or more usually square or rectangular, backinglayer (342) and a chamber (363) in the form of a deeply indented discmuch like a multiple Maltese cross or a stylised rose.

This is defined by an upper impervious membrane (361) and a lower porousfilm (362) with apertures (364) that deliver the irrigant fluid directlyto the wound bed over an extended area, and thus effectively forms aninlet manifold. Three configurations of the chamber (363) are shown inFIG. 6 b, all of which are able to conform well to the wound bed by thearms closing in and possibly overlapping in insertion into the wound.

The space above the chamber (363) is filled with a wound filler (348)under the backing layer (342).

This comprises an oblately spheroidal conformable hollow body, definedby a membrane (349) that is filled with a fluid, here air or nitrogen,that urges it to the wound shape.

A moulded hat-shaped boss (351) is mounted centrally on the upperimpervious membrane (361) of the chamber (363). It has three internalchannels, conduits or passages through it (not shown), each with entryand exit apertures.

The filler (348) is attached to the membrane (361) of the chamber (363)by adhesive, heat welding or a mechanical fixator, such as a cooperatingpin and socket.

An inflation inlet pipe (350), inlet pipe (346) and outlet pipe (347)pass under the edge of the proximal face of the backing layer (342) ofthe dressing, and extend radially immediately under the filler (348) andover the membrane (361) of the chamber (363) to each mate with an entryaperture in the boss (351).

An exit to the internal channel, conduit or passage through it thatreceives the inflation inlet pipe (350) communicates with the interiorof the hollow filler (348), to permit inflation.

An exit to the internal channel, conduit or passage that receives theinlet pipe (346) communicates with the interior of the chamber (363) todeliver the irrigant fluid via the chamber (363) to the wound bed overan extended area.

Similarly, an exit to the internal channel, conduit or passage thatreceives the outlet pipe (347) communicates with the space above thechamber (363) and under the wound filler (348), and collects flow ofirrigant and/or wound exudate radially from the wound periphery.

At its distal end furthest from the wound), the inlet pipe (346) ispermanently attached to, and communicate with the interior of, arecirculation tube (413) in the form of a spiral or loop or a moreconvoluted form. This is a meandering, tortuous or winding path (notshown) sandwiched between parallel electrically heated plates ofresistive conductive material, such as a resistive alloys (also notshown), all within a moulded disc-shape housing case (416).

This has entry and exit apertures in the edge extending between thefaces of the case, through which the irrigant tubing passes. The heatedplates connected to a cell (419) shown schematically, which applies avoltage drop over them in use.

The boss (351) mounted centrally on the upper impervious membrane (361)of the chamber (363) may also include a lumen through it (not shown inthe Figure) with entry and exit apertures. A fourth pipe may also passunder the edge of the proximal face of the backing layer (342) of thedressing, and extend radially immediately under the filler (348) andover the membrane (361) of the chamber (363) to mate with the lumenentry aperture in the boss (351).

An exit to the internal channel, conduit or passage through it thatreceives this pipe may communicate with the space above the chamber(363) and under the wound filler (348), to permit the monitoring ofwound pressure.

Referring to FIG. 7, the apparatus (1) for aspirating, irrigating and/orcleansing wounds is a variant of the apparatus (1) of FIG. 1.

It has bypass (711) around the pump (17), as a protection of the pumpagainst any blockage in the system.

It is activated automatically by appropriate means, e.g. it is normallyblocked by a bursting disc (not shown), or a pressure-activatedmotorised valve.

An alternative to the by-pass (711) is a pressure sensor for themonitoring of pressure in the system and a control feedback circuit forits regulation, e.g. a pressure sensor at a point in the wound space forthe monitoring of negative pressure there, which communicates with acontrol feedback circuit that will shut down the pump when the sensordetects excessive negative pressure. Such a pressure sensor for themonitoring of pressure in the system and a control feedback circuit forits regulation is depicted in FIG. 9.

Another alternative to the by-pass (711) is a pressure sensor mounteddownstream of the pump for the monitoring of positive pressure there,which communicates with a control feedback circuit that will shut downthe pump when the sensor detects excessive positive pressure fromresistance, e.g. in the means for fluid cleansing that is likely tocause the system to fail catastrophically (e.g. burst tubes).

Referring to FIG. 8, the apparatus (1) for aspirating, irrigating and/orcleansing wounds is a variant of the apparatus (1) of FIG. 2.

The latter is a two-phase system with a dialysis unit (21), but is onein which dialytic fluid passes only once across the surface of thedialytic membrane (28) in the first chamber (25) from a dialysatereservoir (not shown) to waste via a second bleed T-valve (36) into,e.g. a collection bag (not shown).

This variant has a dialysate recirculation tube (811) running between afirst T-valve (816) on the inlet side of the dialysate pump (23) and asecond T-valve (817) to permit the pump (23) to recirculate thedialysate once the circuit is primed in multiple passes through thedialysis unit (21).

The operation of the system will be apparent to the skilled person.

Referring to FIG. 9, the apparatus (1) for aspirating, irrigating and/orcleansing wounds is a major variant of the apparatus shown in FIG. 1.

The device for moving fluid through the wound and means for fluidcleansing (17) in FIG. 1 is a peristaltic pump (18), e.g. preferably asmall portable peristaltic pump, acting on the fluid circulation tube(13) downstream of the dressing (2) to apply an overall low negativepressure in the wound space.

In the apparatus (1) shown in FIG. 9, the peristaltic pump (18) isreplaced by:

-   a) a peristaltic pump (926) acting on the fluid supply tube (7)    upstream of the dressing (2), and-   b) a vacuum pump assembly (918) with pressure regulating means,    acting on the fluid circulation tube (13) downstream of the dressing    (2),

to apply an overall low negative pressure in the wound space.

The vacuum pump assembly comprises a tank (911) with

-   an inlet tube (912) connecting to the fluid circulation tube (13)    and communicating with the upper part of the tank (911),-   a waste tube (913) connecting to a waste pump (914) with waste bag    (915) and communicating with the lower part of the tank (911),-   a pump tube (917) connecting to a vacuum pump (918) and    communicating with the upper part of the tank (911), and connecting    via the fluid circulation tube (13) to the means for cleansing (17)    and communicating with the lower part of the tank (911).

The vacuum pump (918) is controlled by a pressure feedback regulator(919) through an electrical line (920), the regulator receiving signalsfrom a tank sensor (921) in the upper part of the tank (911), and adressing sensor (922) in the wound space respectively via lines (923)and (924).

The waste pump (914) is controlled by a waste level feedback regulator(929) the regulator receiving signals from a tank sensor with electricalline (930) in the middle part of the tank (911).

The vacuum pump (918) either acts as a valve so that the pump tube 917connecting to the vacuum pump (918) is normally blocked to preventpassage of air through it from the upper part of the tank (911) when thevacuum pump (918) is at rest, or the pump tube (917) is provided with amanual or motorised, e.g. pressure-activated motorised, valve (930) (notshown), so that the pump tube (917) connecting to the vacuum pump (918)may be blocked to prevent such passage.

The operation of the apparatus (1) is similar to that of the apparatusin FIG. 1 mutatis mutandis.

In use of the apparatus (1), the valve (16) is opened to a collectionbag (not shown), and the T-valve (14) is turned to admit fluid from thefluid reservoir to the wound dressing through the fluid supply tube (7)and inlet pipe (6).

The pump (926) is started to nip the fluid recirculation tube (7) withthe peripheral rollers on its rotor (not shown) to apply a low positivepressure on the wound.

The vacuum pump (918) either acts as a valve since it is at rest, or thevalve (930) (not shown) is closed, so that the pump tube (917) isblocked to prevent passage of air through it from the upper part of thetank (911).

Irrigant pumped from the wound dressing (2) through the fluid offtaketube (10) is pumped through the lower part of the tank (911) up theoutlet tube (917) via the means for cleansing (17) to the bleed T-valve(16) into, e.g. a collection bag (not shown).

The peristaltic pump (926) acting on the fluid supply tube (7) upstreamof the dressing (2) is allowed to run until the apparatus is primedthroughout the whole length of the apparatus flow path and excess fluidis voided to waste via the bleed T-valve (16) into the collection bag.

The T-valve (14) is then turned to switch from supply to recirculation,i.e. is set to close the wound to the fluid reservoir (12) but to admitfluid into the wound from the fluid recirculation tube (13), and thebleed T-valve (16) is simultaneously closed.

The vacuum pump (918) is then activated, and, if the vacuum pump (918)does not act as a valve when at rest, the valve (930) in the pump tube(917) is opened, to apply a low negative pressure to the wound.

The circulating fluid from the wound and the fluid reservoir (12) passesthrough the cleansing unit (17). Materials deleterious to wound healingare removed and the cleansed fluid, still containing materials that arebeneficial in promoting wound healing, is returned via the recirculationtube (13) to the wound bed.

The pressure feedback regulator (919) regulates the pressure at thewound and/or the tank (911).

If the amount of fluid in circulation becomes excessive, e.g. becausethe wound continues to exude heavily, the waste pump (914) may bestarted by the waste level feedback regulator (929) on the regulatorreceiving signals from the tank sensor with electrical line (930).

The recirculation of fluid may be continued as long as desired.

The vacuum pump (918) is then deactivated, and, if the vacuum pump (918)does not act as a valve when at rest, the valve (930) in the pump tube(917) is closed, and the bleed T-valve (16) is opened to air to relievethe low negative pressure in the tank (911) via the means for cleansing(17) and the outlet tube (917).

Switching between supply and recirculation is then reversed, by turningthe T-valve (14) to admit fluid from the fluid reservoir to the wounddressing through the fluid supply tube (7) and inlet pipe (6).

The bleed valve (16) is left open, so that fresh fluid flushes therecirculating system. The running of the pump (918) may be continueduntil the apparatus is flushed, when it and the fluid recirculation isstopped.

The use of the apparatus of the present invention will now be describedby way of example only in the following Example:

EXAMPLE 1 The Combination of the Removal by Dialysis of MaterialsDeleterious to Wound Healing (H₂O₂) by an Enzyme (Catalase) Retained ina Moving Second Phase and the Transmission of Heat to a Moving FirstPhase

An apparatus of the present invention was constructed essentially as inFIG. 2, i.e. one in which the means for fluid cleansing is a two-phasesystem dialysis unit. In such an apparatus, an irrigant and/or woundexudate first phase from the wound recirculates through a first circuitand passes in through the dialysis unit in contact across a selectivelypermeable dialysis membrane with a second fluid (dialysate) phase. Thedialysis unit was operated with the two phases flowing counter-currentto each other.

Hydrogen peroxide is produced in conditions of oxidative stressfollowing reduced blood flow and or the inflammatory response tobacterial contamination of wounds. It may be removed by the appropriateantagonists and/or degraders, which include enzymic or other inhibitors,such as peroxide degraders, e.g. catalase.

The first circuit comprised a surrogate wound chamber (Minucellsperfusion chamber) in which normal diploid human fibroblasts werecultured on 13 mm diameter (Thermanox polymer) cover slips retained in atwo-part support (Minnucells Minusheets). Tissues present in the healingwound that must survive and proliferate were represented by the cellswithin the chamber. Nutrient medium (DMEM with 10% FCS with 1% BufferAll) to simulate wound exudate was pumped from a reservoir into thelower aspect of the chamber where it bathed the fibroblasts and wasremoved from the upper aspect of the chamber and returned to thereservoir.

The first circuit also comprised

-   a) Upstream of the wound chamber, a luer-fitting hollow fibre    tangential membrane dialysis unit (Spectrum® MicroKros®    X14S-100-04N, 8 cm² surface area, 400 KD Mol. Wt. cut off,) through    which a second cleansing circuit containing nutrient media with    between 5,000 and 50,000 units (μ moles H₂O₂ degraded per min at    pH7, 25° C.) per ml of catalase (in a circuit with a reservoir and    total volume of between 5.0 mL and 20 mL) at a flow rate of between    0.5 ml min⁻¹ and 5.0 ml min⁻¹ could be passed in a counter current    direction, and-   b) upstream of the wound chamber, a heat exchanger such that the    temperature of the nutrient media bathing the cells reaches between    35° C. and 37° C.

The pumps for the two circuits were peristaltic pumps acting on siliconetubing or equivalent. The internal diameter of the tubing was 1.0 mm. Atotal volume for the first circuit including the chamber and thereservoir at a number of values between 25 and 75 ml was used. The flowrates used were at a number of values between 0.5 ml min⁻¹ and 5.0 mlmin⁻¹.

Experiments were conducted that simulated conditions not uncommon forhealing wounds whereby the chamber simulating the wound was placed in aroom temperature environment (simulating the low temperatures oftenexperienced in wounds where blood flow is poor) and the nutrient mediumcontaining a material deleterious to wound healing, namely hydrogenperoxide, was circulated over the cells.

First and second control apparatus were also constructed essentially asin FIG. 2, but where either

-   a) the cleansing membrane dialysis unit is omitted, so that the    nutrient flow passes directly from the reservoir, or-   b) the heat exchanger is omitted, so that the nutrient flow bathing    the cells does not reach between 35° C. and 37° C. and remains at    between 18° C. and 20° C.

In controls where either

-   a) the passage of the nutrient flow through the cleansing membrane    dialysis unit or-   b) the heat exchanger unit is omitted,

and the concentration of H₂O₂ lies between 5 and 20 mM and thetemperature of the nutrient medium bathing the cells is between 18° C.and 20° C., survival and growth of the fibroblasts is inhibited.

However, when the nutrient medium flow in the first circuit is

-   c) connected into the ends of the membrane dialysis unit through    which a second cleansing circuit containing catalase (at the    concentrations and flow rates noted above) is passing in a counter    current direction, and-   d) passes through a heat exchanger so that the temperature of the    nutrient media bathing the cells reaches between 35° C. and 37° C.,

the fibroblasts survive and proliferate to a greater extent during a 24hour period than the control circuits.

EXAMPLE 2 The Combination of the Removal by Dialysis of MaterialsDeleterious to Wound Healing (H₂O₂) by an Enzyme (Catalase) Retained ina Static Second Phase and the Transmission of Heat to a Moving FirstPhase

An apparatus of the present invention was constructed essentially as inFIG. 2, i.e. one in which the means for fluid cleansing is a two-phasesystem dialysis unit. In such an apparatus, an irrigant and/or woundexudate first phase from the wound recirculates through a first circuitand passes over the dialysis unit in contact across a selectivelypermeable dialysis membrane with a second static fluid (dialysate)phase.

Hydrogen peroxide is produced in conditions of oxidative stressfollowing reduced blood flow and or the inflammatory response tobacterial contamination of wounds. It may be removed by the appropriateantagonists and/or degraders, which include enzymic or other inhibitors,such as peroxide degraders, e.g. catalase.

The first circuit comprised a surrogate wound chamber (Minucellsperfusion chamber) in which normal diploid human fibroblasts werecultured on 13 mm diameter (Thermanox polymer) cover slips retained in atwo-part support (Minnucells Minusheets). Tissues present in the healingwound that must survive and proliferate were represented by the cellswithin the chamber.

Nutrient medium (DMEM with 10% FCS with 1% Buffer All) to simulate woundexudate was pumped from a reservoir into the lower aspect of the chamberwhere it bathed the fibroblasts and was removed from the upper aspect ofthe chamber and returned to the reservoir.

The first circuit also comprised

-   a) for the static second phase, a length of dialysis tubing (Pierce    Snake skin 68100 CG 49358B, 10 KD cut off) placed within the first    circuit reservoir in which a second static cleansing circuit    containing nutrient media with between 5,000 and 50,000 units (μ    moles H₂O₂ degraded per min at pH7, 25° C.) per ml of catalase (in a    circuit with a reservoir and total volume of between 5.0 ml and 20    ml)-   b) upstream of the wound chamber, a heat exchanger such that the    temperature of the nutrient media bathing the cells reaches between    35° C. and 37° C.

The pumps for the circuit were peristaltic acting on silicone elastictubing or equivalent. The internal diameter of the tubing was 1.0 mm. Atotal volume for the first circuit including the chamber and thereservoir at a number of values between 25 and 75 ml was used. The flowrates used were at a number of values between 0.5 ml min⁻¹ and 5.0 mlmin⁻¹.

Experiments were conducted that simulated conditions not uncommon forhealing wounds whereby the chamber simulating the wound was placed in aroom temperature environment (simulating the low temperatures oftenexperienced in wounds where blood flow is poor) and the nutrient mediumcontaining a material deleterious to wound healing, namely hydrogenperoxide, was circulated over the cells.

First and second control apparatus were also constructed essentially asin FIG. 2, but where either

-   e) the cleansing membrane dialysis unit is omitted, so that the    nutrient flow passes directly from the reservoir, or-   f) the heat exchanger is omitted, so that the nutrient flow bathing    the cells does not reach between 35° C. and 37° C. and remains at    between 18° C. and 20° C.

In controls where either

-   a) the passage of the nutrient flow past or through the cleansing    membrane dialysis unit or-   b) the heat exchanger unit is omitted,

and the concentration of H₂O₂ lies between 5 and 20 mM and thetemperature of the nutrient medium bathing the cells is between 18° C.and 20° C., survival and growth of the fibroblasts is inhibited.

However, when the nutrient medium flow in the first circuit is

-   c) passed over the membrane dialysis unit in which a second    cleansing circuit containing catalase (at the concentrations and    flow rates noted above) is present, and-   d) passes through a heat exchanger so that the temperature of the    nutrient media bathing the cells reaches between 35° C. and 37° C.,

the fibroblasts survive and proliferate to a greater extent during thanthe control circuits.

The following results were obtained: A first phase of nutrient mediumcontaining 10 μM H₂O₂ at a flow rate of 1.0 ml min⁻¹ with a 15 ml staticsecond phase containing 7,600 units ml⁻¹ catalase contained within alength of dialysis tubing placed within the first circuit reservoir. Theeffect of the catalase cleansing unit and the heat exchanger was asfollows:

Mean level of cell activity after 43 hrs* Conditions (n = 6) H₂O₂ inmedia at 18° C. 0.0 H₂O₂ in media with catalase second 0.27 phasedialysis unit at 18° C. Normal medium control at 18° C. 0.40 H₂O₂ inmedia at 37° C. 0.0 H₂O₂ in media with catalase at 37° C. 0.76 secondphase dialysis unit Normal medium control at 37° C. 0.55 *Cell activitymeasured with WST (Tetrazolium based mitochondrial dehdrogenase activityassay)

CONCLUSIONS

The combination of the cleansing dialysis unit that removes and degradesH₂O₂ and the heat exchanger unit that maintains the wound chamberbetween 35° C. and 37° C. enhances the cell response necessary for woundhealing.

1. An apparatus for irrigating, supplying thermal energy to, andcleansing wounds, comprising: a fluid flow path, comprising: aconformable wound dressing, comprising a backing layer which is capableof forming a relatively fluid-tight seal or closure over a wound and awound-facing face, at least one inlet pipe passing through and/or underthe wound-facing face and directly or indirectly communicating with atleast a fluid reservoir, and at least one outlet pipe passing throughand/or under the wound-facing face, wherein a relatively fluid-tightseal or closure is formed over the wound at the point at which eachinlet pipe and each outlet pipe passes through and/or under thewound-facing face; a means for fluid cleansing in direct or indirectcommunication at least with the outlet pipe; and a fluid recirculationtube for directing cleansed fluid from the means for fluid cleansingback into the inlet pipe without passing through the reservoir so thatat least nutrients, molecules, factors, physiologically activecomponents and/or other components from the wound dressing that aid inproliferation or that are favorable to the wound healing process arereturned to the wound; a device for moving fluid through at least thewound dressing and the means for fluid cleansing; a means for supplyingthermal energy to at least the recirculated fluid provided to the woundso as to maintain the wound at a temperature between 34 and 40 degreesCelsius to optimize the metabolic activities of physiologically activecomponents within the wound dressing and promote wound healing, and ameans for bleeding the fluid flow path to bleed fluid from therecirculation tube to relieve pressure within the fluid flow path.
 2. Anapparatus according to claim 1, wherein the means for supplying thermalenergy to the fluid provided to the wound comprises a heater and/or aconductively heated component of the apparatus flow path.
 3. Anapparatus according to claim 1, wherein the means for supplying thermalenergy to the fluid provided to the wound comprises a radiative heater.4. An apparatus according to claim 1, wherein the means for supplyingthermal energy to the fluid provided to the wound comprises aconductively heated component of the apparatus flow path and a radiativeheater.
 5. An apparatus according to claim 1, wherein the means forfluid cleansing is a single-phase system, in which circulating fluidfrom the wound passes through the means for fluid cleansing andmaterials deleterious to wound healing are removed without thecirculating fluid coming into direct or indirect contact with anotherfluid in the means for fluid cleansing.
 6. An apparatus according toclaim 1, wherein the means for fluid cleansing is a two-phase system, inwhich circulating fluid from the wound passes through the means forfluid cleansing and materials deleterious to wound healing are removedby the circulating fluid coming into direct or indirect contact withanother fluid in the means for fluid cleansing.
 7. An apparatusaccording to claim 6, wherein the circulating fluid from the wound andthe other fluid in the means for fluid cleansing are separated by aninteger which is selectively permeable to materials deleterious to woundhealing.
 8. An apparatus according to claim 6, wherein the circulatingfluid from the wound and the other fluid in the means for fluidcleansing are separated by an integer which is not selectively permeableto materials deleterious to wound healing, and the other fluid comprisesand/or is in contact with a material that removes materials deleteriousto wound healing.
 9. A method of treating wounds to promote woundhealing using the apparatus for aspirating, irrigating and/or cleansingwounds according to claim
 1. 10. An apparatus according to claim 1,wherein the means for supplying thermal energy comprises a heaterconfigured to supply thermal energy to fluid in the at least one inletpipe.
 11. An apparatus according to claim 1, wherein the apparatus isconfigured such that at least a portion of fluid flowing through theoutlet pipe is directed to a waste reservoir.
 12. A method of treating awound, comprising: providing a conformable wound dressing having a coverconfigured to form a relatively fluid-tight seal around at least aportion of a wound; providing an apparatus for irrigating and/orcleansing a wound comprising: at least one inlet pipe configured tocommunicate with the cover and configured to provide a fluid conduitbetween at least a fluid reservoir and the cover so that fluid can flowinto the cover; and at least one outlet pipe configured to communicatewith the cover and configured to provide a fluid conduit so that fluidcan flow out of the cover, wherein the fluid in the cover comprisesphysiologically active components; pumping fluid through at least theinlet pipe, the cover, and the outlet pipe; cleansing the fluid thatflows out of the cover; regulating the fluid that flows out of the coverso that a portion of the fluid that flows out of the cover comprisingphysiologically active components is recirculated back to the coverwithout passing through the reservoir after being cleansed and a portionof the fluid that flows out of the cover is bled through a bleedmechanism and is provided to a waste reservoir to relieve pressurewithin the cover; and heating the fluid before the fluid enters thecover to maintain the wound at an approximately normothermic range tooptimize the metabolic activities of the physiologically activecomponents within the cover and promote wound healing.
 13. The method ofclaim 12, wherein the normothermic range is from approximately 34 and 40degrees Celsius.
 14. The method of claim 12, further comprisingadjusting the proportion of the amount of fluid that is provided to thecover after being cleansed and the amount of fluid provided to the coverfrom the fluid reservoir.
 15. An apparatus for irrigating, supplyingthermal energy to, and cleansing wounds, comprising: a wound dressingcomprising a backing layer configured to form a relatively fluid-tightseal around at least a portion of a wound; at least one inlet pipeconfigured to communicate with the backing layer and to provide a fluidconduit into the backing layer; at least one outlet pipe configured tocommunicate with the backing layer and to provide a fluid conduit out ofthe backing layer; a fluid reservoir comprising irrigation fluid influid communication with the inlet pipe to supply irrigation fluid fromthe fluid reservoir into the backing layer; a fluid pump configured topump fluid through at least the inlet pipe, the backing layer, and theoutlet pipe; a fluid cleansing mechanism in fluid communication with theoutlet pipe; a recirculation tube in fluid communication with the fluidcleansing mechanism configured to recirculate fluid cleansed by thefluid cleansing mechanism back into the inlet pipe without passingthrough the fluid reservoir, the fluid recirculation tube having a bleedvalve to bleed fluid from the recirculation tube to relieve pressurewithin at least a portion of the apparatus, the recirculated fluidcomprising physiologically active components; and a heat sourceconfigured to heat at least the recirculated fluid before the fluidenters the backing layer, the heat source configured so that the fluidmaintains the wound at an approximately normothermic range to optimizethe metabolic activities of physiologically active components within thebacking layer and promote wound healing.
 16. An apparatus according toclaim 15, wherein the thermal energy provided to the wound maintains thewound between approximately 34 and 40 degrees Celsius.
 17. An apparatusaccording to claim 15, wherein the heat source comprises a radiativeheater.
 18. An apparatus according to claim 1, wherein the means forsupplying thermal energy to the fluid provided to the wound is supportedby the backing layer.
 19. An apparatus according to claim 1, wherein themeans for supplying thermal energy to the fluid provided to the wound isconfigured to surround at least a portion of at least one inlet pipe.20. The method of claim 12, comprising heating the fluid before thefluid enters the cover with a heat source supported by the cover. 21.The method of claim 12, comprising heating the fluid before the fluidenters the cover with a heat source surrounding at least a portion ofthe at least one inlet pipe.
 22. An apparatus according to claim 15,wherein the heat source is supported by the backing layer.
 23. Anapparatus according to claim 15, wherein the heat source is configuredto surround at least a portion of the inlet pipe.